Does anypony really know?

[The Wandering Magus]

I personally just assumed that they were between the pony equivalent of 18 to 26 year old humans and just sort of left it at that. Old enough to have jobs, but still young enough to have a lot to learn about the world.

If I were to give a rough guess though I honestly think pinkie and twilight seem to be the youngest of the bunch, with fluttershy and rainbow in the middle and rarity and applejack being easily the oldest. But that's just a rough guess from my personal opinion.

As for lifespans I figured earth pony's would have something similar to horses and ponies on our world while pegasi would have slightly longer lifespans and unicorns having the longest (with the exception of alicorns of course).

All personal opinions though with a lot of speculation since until actual ages are given out there's no real fact to go on.

well we also know that the Cakes twins are a month old.  Now, judging from their physical and mental development, what does that tell you about their lifespan?

Also taking onto account how long it takes for an advanced brain like mlp ponies or humans to process and utilize information from experiences etc.  And how long it generally takes to acquire an advanced language, for any sapient or near-sapient animal.