How much time can you burn RW?

[Neoh]

The title says it all, about how many times can you burn a DVD+RW before having trouble with it?(less space, etc, like a CD-RW)

I got a Sony DVD+RW and allready recorded like 10 times on it (DVD movies) and now the end of the movies are jiggery, want to know if this is due to the fact i burned it too many times or my encoding (I didn't change my way to do it though.)

[Neoh]

ok I tested the same movie on a +R and all works well, is there a way to format the DVD+RW totaly (in nero or RecordNow the formating of a DVD+RW takes only a few seconds it seems a bit short to me)