I don't mean the difference between old pages and new but between storyteller Alan and flashback Allan - he does look notably younger (usually young people tend to have somewhat softer look to them - more fat on cheeks, less sharp nose and chin etc.) between first page and the rest in mercy 006-017 so I do' t think it is the beard. I was worried about something like accidental age slip in the last few strips but probably it might be just a style drift as you say. By the way, I know some people my age that have barely changed in the last 10 years - some of them are still stuck with babyface at 30+ (myself included), while others looked like they were at least in their midtwenties when in fact they were around 18. So yeah, if he looks like you want him to look, all is fine. Have fun!