I can't help much on the time lag although 6 minutes does seem to be a very long time. As far as the recirculating system is concerned, I can just relate my own experience. I have been using a recirculating system for about 4 years and I never turn the pump off. I'm sure there is more wear on the pump doing this, but I figure that the added wear plus the small increase in electricity is just the price of have instant hot water anytime day or night. I have no clue as to how much the electricity costs per month to run that small motor, but it can be much. I will have to admit that I don't have anywhere near the size house you have, and perhaps that will make some difference although I don't really see how it would cost more to operate. Be sure you insulate the hot water pipes both on the supply side and the return line.
I'll be watch this thread to see what opinions the pros offer on the time lag without the recirculating pump.