When is it OK to use a Disposable (Landfill) Diaper?

I’ve always professed that every baby should wear cloth diapers; however, with my son wearing one diaper in 24 hours, it takes a long time to make a diaper load of laundry. After a week, these cloth diapers get very rank, and I don’t really want to put them in my washing machine or waste energy and water to wash them more often.  Thus, I’ve resorted to Seventh Generation’s Chlorine-Free Diapers, as it is too late in the game (I don’t plan to have any more children  ) to invest in gDiapers. I do feel a slight pang of guilt using a landfill, aka disposable, diaper, but I rationalize six years of cloth diapering two kids has earned me the right to one disposable diaper a day.