🚀 go-pugleaf

>>   The question is:  Is it safe to reuse mag tapes for important data...

>				...it is generally accepted that used but not
>worn-out tapes are best for archival storage.  Has something to do with the 
>original-factory-fresh erasing done, and that it takes several recording
>erasing cycles to make the tape really "take" a recording well.

Nonsense. Every single pass degrades tape through friction and tension
(shuttle on a poorly designed transport is hell on tape).
For that matter, the heads get worn and/or clogged also. Oxide comes
off, the substrate stretches, etc. Each pass brings the tape closer
to death, and statistically increases chances for droupout (the
bugaboo of digital tape) and so forth. In the world of magnetic
recording, unlike life, the first time is not only the best,
it's also completely forgettable.

With that said, I must also point out that the degradation experienced
each pass varies depending on tape and transport, but by and large
the first (say) dozen passes on a GOOD recorder SHOULD produce 
unnoticeable changes in the quality of a GOOD tape. 

This is as I heard it at Ampex. 3M might tell you differently.

--Mike Tuciarone
  tooch@sun