I've been brewing for seven years and I probably do mini-mashes more than anything else. With 4-5 pounds of grain, I mash with 2.5 gallons of water, mix in the extract and start heating the wort while batch sparging with another 3 gallons. I don't have to pay any attention to the tun & drain it after 15 minutes. The first runnings will be near boiling, so when I add the second run the wort is around 180F.
No extra boil time is needed to concentrate the wort and I get very good efficiency.
I routinely do a batch of ale in under 3 hours. Figure $3-4 extra for the extract over all grain, but I probably get a buck back on reduced propane usage.