All of the previous suggestion have merit. I believe the best solution is to use a recirculation pump with a return line. Certainly there are installation concerns that may make this impractical, but if at all possible, I'd go with that method. I installed this kind of system in my home several years ago and it really works great. It is a Laing pump and it runs 24/7. I could use a timer, but I like the instant hot water when ever I want it, so no timer for me.