@Background Pony #789B  

In Dragonshy Celestia told Twilight dragons can easily NAP for 100 years.  
I really doubt a creature whose mere naps can last 100 years, have lifespans in the 100-1000 range.  
I’d say its probably on the 10,000-100,000 years at least.

@SingleCrystal  
I was just joking, I barley know how to spell DND.

@MadVillan  
It’s from D&D 3.5, which Pathfinder borrowed from.
 
http://www.d20srd.org/srd/monsters/dragonTrue.htm

@Vree  
So.  
A dragon lives 100+ years.  
Celestia is a alicorn and have more than 1000 years.  
Twilight being a alicorn like celestia,from a unicorn.  
Rarity is a unicorn, if she become a alicorn the ship have no problems.

@Background Pony #E951  
Hard to say. Personally, I like the headcanon that non-greed-growth dragons mature just as fast as their greed-growth counterparts but keep growing past maturity into what we would call an “adult” size. Kinda like certain species of turtle. But, y’know, aside from knowing that some dragons can reach adulthood instantly if they give into greed and that some dragons can remain small after 10-15 years, everything concerning MLP dragon lifecycles is pretty sparse.

I think this rule doesn’t apply as maturity of a dragon is based on their greed at some point. Spike could’ve been older then the dragons that bullied him.

@bico-kun  
But that could easily be due to how much he’s lived. Considering G4 Spike’s size means he’s a baby and how big dragons get, its unlikely that G4 Spike was already “juvenile” or even close to that. He was still overall smaller than a pony, which based on the previous examples, for me translates to baby or young kid at least.
 
I mean, both Spike’s are way more mature than what their size, in comparition to adults of their race, would suggest of their age. So either a dragon’s mental development is as fast as the shorter-lived races despite their bodies taking way longer to develop, or its something that only happens due to living among ponies.

@Background Pony #E951  
Well, G3 Spike said he was still young, not a baby. He definitely seemed to be portrayed as more adult than the ponies in that series.

And yet the fact that the D&D dragons in those age categories are already much bigger than that (they’re born bigger than Spike’s current size) and also that they said MLP dragons usually take 100-year naps, means that these age categories probably don’t apply in this universe. If we go further and add G3 Spike into the mix (who was already over a thousand and still a baby) then it gets even worse. MLP Dragons seem to mature really slow.

@bico-kun  

 
Or ponies in this world are actually the size of massive draft horses, and everything we’ve been told to believe is a lie! A LIE!
 
Yes, I did just wake up and no, I haven’t had enough tea yet XD

Of course, Young Dragons generally are said to leave their parents and live on their own due to their greed and hoarding instincts being kicked into overdrive. Now, if one were to use this dragon aging chart as headcanon for MLP dragons, it would seem that Spike must have hit 16 on his last canonical birthday, which matches up with @TheDeinonychus’ observation on the age gap between Spike and Twilight. One could also take from the description of the Dragon Life Cycle that Young Dragons are more equivalent to what humans would call young adults.
 
Of course, even a Wyrmling should apparently be between the size of a large wolf and a full grown human while a Young Dragon would be the size of a full-sized horse. Apparently, by this canon, Spike is puny even by dragon standards.
 
Or the writers could just be making it up as they go along.

@superdarklink  
At the same time, though, they readily admit to not knowing much about dragons. Could be them speaking about his size relative to other dragons (Which we have seen isn’t always about age)

@TheDeinonychus  
Don’t they refer to him as a baby dragon multiple times though? Which would mean that he ages even slower tan that.

And then they can /ss/

This (along with most speculation on age) all depends on two main things. Firstly, that ponies in MLP age at roughly the same rate as humans, rather than real-world ponies. Otherwise, by this chart, Rarity would be long dead by the time Spike is even considered a ‘young’ dragon.  
Secondly, it also depends on what age you believe Twilight was when she took her magic test. If we assume that ponies do age like humans, then Twilight living on her own would indicate that she’s an adult, somewhere around the age between 18 and 20 at the start of the series. If you assume that Twilight was about 5 years old (the age where children enter grade school), that would make Spike 15 years old at the start of the show. That would make him about 20 now. If you go with Twilight being around the age of 10 when she took her magic test (the age most children enter middle school), he would still be about 15.  
This brings up an issue. In the episode ‘Dragon Quest’, Spike refers to the other dragons as ‘teenaged’. Yet, in raw numbers, he himself is a teenager in the show. For this to not be a complete oversight on the part of the writers, you would have to assume that all dragons use a different measurement of time compared to the seasonal measurement that the ponies use (where every four seasons is a distinct year). If, for the sake of argument, we go with the dragons in that episode being ‘young adult’ to equate that with being ‘teenaged’, that would mean a ‘dragon year’ happens roughly every 4 pony years. That would make Garble and his friends between the ages of 13 and 25. Spike, by contrast, would only be about 4 or 5 years old (depending on how old Twilight was when he hatched) in dragon years.

@MadVillan  
Well, Pathfinder is basically Dungeons & Dragons with another name so… and it mens you roll 12 four sided dices and ad 4 to that to know how much damage it does

Soon:  

@MadVillan  
That’s like the difference between calling it “an applefritter” and “a deep-fried, apple-based, baked good”. :p
 
 
@Background Pony #5758  
So basically in 80ish years Rarity can snuggle him without being creepy.

THANK YOU! SOMEBODY ELSE WHO FOLLOWS THIS HEAD CANON!

Okay, so G3 Spike lied about being quite young, he’s actually a great wyrm who can apparently live up to age one million+.

Make a wish?

@Soarinjack
 
@Kolbjorn  
Um Actually it’s from Pathfinder, casuals. And Spikes breath attacks are already at least Young dragon level. Hence when Equestria games when his breath did 12d4+6 damage to the glacier.  
|| I have no idea what I’m talking about||

@Background Pony #12B5  
Probably Dungeons & Dragons

@Background Pony #12B5  
Dungeons & Dragons 3.5e.

What’s the chart from?