yeah, but it doesn't really matter how old the actor is, it's how old he looks/is portrayed for the character. In that final shot in ROTJ, i would never know that Sebastian Shaw was older than Alec Guinness just by looking, so why does it matter? by that point Anakin would've been an older gray man just like Obi-wan anyway, so it looked fine to me & i'm willing to accept that Obi-wan was the older of the two in the movie.