tes,
I have read several posts from video pros saying that the Panasonic Professional tapes are among the most reliable. But I sure wouldn't re-record over them for hundreds of times. As you run a tape over the record heads, it does wear on the tape; and, after a while, particles will come loose from the tape. Some of these tiny particles will find their way into the gap in the record head. Eventually you'll have a clogged head, which causes glitches in the recording. Also, the worn-out tape can have drop outs where the particles have flaked off. This is more evident in HDV, but even with standard def it can be a problem. My policy is to never (well, ALMOST never) re-record.
Ken Hull