I feel like age is irrelevant in the theatre-- after all, the great Sarah Bernhardt could play a young boy when she was in her eighties-- as long as the performers are good actors. It's the suspension of disbelief, like having characters of different races playing biological family members. I know absolutely nothing about Rent, so I can't say anything about how good the performers are, but I wouldn't say someone was 'too old' for a role.
I do have to say, though, are cheering during a performance and being asleep during a performance the only options? I've rarely seen anyone do either at any of the shows I've been to. (Except for my brother, who comes to every show I'm in and always falls asleep during the first five minutes.)
In my pants, she has burst like the music of angels, the light of the sun! --Marius Pantsmercy