D.B.
Hi JB,
The good news is that the 5 month old will most likely nap for at least half of that time (on and off). I agree to stop and "exercise" his/her legs and allow time for stretching out for the both of you. Have lots of little noise maker toys for your child to play with and throw around a little. Kid Music and book on tape for Mommy sounds like a good idea. Good luck!
D.