My headcanon is that unicorns have much longer lifespans than the other races, which is an effect magic has on their bodies. Earth ponies live reasonably long lives, with the ones that are connected to the earth via cutie marks (like the Apple family) living even longer - the Apple family etc. Pegasi, being generally lightweight and temperament, have the shortest life spans by far.
 
In most fantasy settings, creatures with magical capabilities have great lifespans. I can picture extraordinarily gifted unicorns (Starswirl, Clover the Clever) living for well over a century.

@Ravebrony42
 
True, its why i also think that Earth ponies can grow the oldest while Unicorns die the earliest.

So sad. Although this does go against my headcannon that earth ponies live longer than the others. We’ve only seen one old pegasus and no old unicorns. But we’ve seen dozens of old Earth Ponies.

@Background Pony
 
I did.

dear OP  
FFS  
Twicorn/Twilight Princessssssssso tag  
>.>