Kristi O'Nan shares a tip that she used in AutoCAD 2008 to speed up screen regens and simplify viewport handling.
"I often make copies of viewports in paper space, and the template that I use had Regenauto set to 'Off.' Every time I would copy a viewport, the copy would be turned off, and I would go through the properties to turn it back on. That was a huge pain to deal with. To avoid having to turn on all copied viewports, set Regenauto to 'On.' This will also end the plague of 'About to Regen' warnings."
Notes from Cadalyst Tip Patrol: I have run into this issue many times. You copy a viewport, only to find out the copied viewport is turned off. While testing this tip, I couldn't duplicate Kristi's results using AutoCAD 2010, so I can't verify that the Regenauto command solves this problem. Regardless, keeping Regenauto turned on is a good idea. It will make sure your file is regenerated whenever AutoCAD wants to perform a regen. Most workstations aren't bogged down by regens like they used to be, but you may have a problem with drawings that reference large image files or if you like to make hatches.