I know it's popular here to shift into neutral in their automatics and I have been at times guilty of doing it as well but I should warn you that there really is a risk to damaging the transmission.
Read this thread about the volvo:http://www.volvoxc.com/forums/showthread.php?t=11149
Basically Volvo cars made between '01-'03 maybe earlier and maybe later had a feature where the car would shift into neutral when you press on the brake and come to a stop in order for the car to save fuel. The car would then shift back into gear when the driver let up on the brake. The problem is, these cars' transmissions would go bad after only 40K miles so Volvo patched the transmission software so that the transmission would always stay in gear and this seems to have resolved the issue with Volvo transmissions prematurely failing.
So just keep in mind that doing such a thing really could cause one's transmission to grenade. The thing I didn't mention though but is in the threads I linked to was that part of the problem was that since it didn't shift into gear until the brake was let up on was that you could get into a situation where the car thinks you want to slow down so it shifts into neutral but then you surprise it by asking to accelerate after a brief moment of deceleration, so it hastily shifts into gear, causing a notorious "clunk" in the transmission to be heard. Despite me being pretty sure my car's software is patched, I've heard this clunk under numerous occasions though it's usually heard when shifting out of reverse and into drive or shifting at the wrong time with the Geartronic. So chalk it up to software or an undersized transmission, fact is, you could put a lot more extra wear on the transmission by shifting back and forth into neutral and drive.
All I can suggest to you is to tread lightly and be able to accept the fact that you may very well damage the transmission or reduce its useful life.