Lots of pressing save, and incremental, save as, is very handy for this reason. you can always erase the ones you don't need any more at the end of the day.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit