NEW YORK (Reuters) - Disposable DVDs may have a short shelf life in more ways than one. With major retailers such as Wal-Mart Stores Inc. (WMT.N) already selling more cut-price DVDs, industry experts say it is far from certain whether consumers would be eager to shell out $7 for a DVD movie they can't keep or watch beyond a 48-hour deadline.This week Buena Vista Home Entertainment, the home video arm of Walt Disney Co. (DIS.N), began distributing a limited number of movie titles on the self-destructing DVD format -- known as EZ-D -- to a few U.S. markets.The EZ-D comes...