I'm in my mid thirties and my BF is in his early fifties also!
I'm surprised that you still get the impression that CDs want to "do it all the time" most never leave the closet and if they do its to venture out to a mall or some CD event and certainly not full time. Anyway if a "CD" wants to dress "full time", there is like a 99% chance they aren't a CD. They are more likely transsexual, like me, which involves a whole lot more than just playing dress up!
obviously you will have to find what your limitations are and express them to your BF. If you don't want to see him dressed tell him! but give him the space to do it because CDing doesn't go away.
Why would you ask someone you love to go without? Tell him your limits and if he loves you he will respect that but give him the same in return.
I think you are WAY over thinking this! You are not gay, he is not gay, hes just a dude that likes to do something that you have never heard of before but is actually a lot more common than people think.
Good luck to you and your BF If he is really that great of a guy I think you owe it to yourself to give him a chance. If he pushes you beyond your limits you can always kick him to the curb later!
April