I asked this about a year ago. I have the DVX100A. I was told it is ok to reuse tapes as long as I am using them for unimportant stuff. Reusing can cause image problems not being as sharp and also causing drop-outs.
As far as camera damage, if you use the same type tape always reuse won't damage it. Just don't go overboard.
its not bad until you do it like a third of fourth time. it stretches the tape a tiny bit, but its enough to make dropouts and glitches slightly more likely.
I have one tape i have reused more than 80 times and it give no dropouts. If tape was made for only one time, it should not go to play it. But i save the original tape.
I hope my English is not to bad :beer:
I just shot a week long horse show using DV Monitor Pro and recording to miniDV as backup. I had just two tapes which I rotated the whole time. After a good 50 or so records the footage still looks free from dropouts, although I didn't review every frame by any means! I would think you'd be okay to reuse tapes in a pinch, but wouldn't recommend it for your money shots. This was with PQ's too, not MQs.
Since the advent of video tape, I've always followed a few rules that have served me well to "stretch" the life of tape, #1) Before using, completely fast-forward and re-wind the tape once to make sure the tape is properly packed. #2) Store it correctly in it's case at an appropriate temp and humidity and on it's side. #3) If tape has sat on shelf awhile, see #1. #4) Minimise pausing, and short re-winds and fast-forwards in reviewing footage in camera. #5) Make sure tape transport is in proper mechanical condition (tensions correct) and that heads and tape path are clean. Tape can last a long while if it's stored and handled correctly. That said, I normally use it once in a critical situation, then use it for things like b-roll shots later. Today, I just pulled a 3/4" tape (camera master) off of the shelf from 1980 that has been properly handled and it looks pretty darn good!