Rayman 1: 6 years
Rayman 2: 10 years
Rayman M: 12 years
Rayman 3: 15 years
In R1, I suppose he was very young because of his basic appearance with the beady eyes and such, and his voice was so high at the time!
In R2, he seems to have matured a bit with the things he tells other characters and he also seems to have greater control over his various powers.
In RM, well he fights and races a lot. Possibly the work of puberty taking effect? Hmm...
In R3, he's clearly in his teenage years. He's more sarcastic in the things he says, his clothes have the look of a teenager (the two pullstrings from his scarf) and his voice is very deep.
Who knows? Maybe in R4 he'll have his driver's license and he'll just be able to run over all the baddies in his tank/monster truck/steamroller.
I think he's immortal, since no one created him.