I think it makes perfect sense that Al's body didn't age while it was in the gate, therefore it also makes sense that he would have no memory of everything that happened...
But I still cant help but wish that he had kept his memory's and gotten older, because he learned some valuble life lessons from everything that happened (especially when Ed died and Al decided to 'give his share' and bring him back)
But at least he got his memories at the end of the FMA movie!!