M H Stein wrote:
  I'm still curious; assuming any useful data has
been archived
 and I just want to reuse the tapes some day, what would
 maximize the chances of their still being useable? Is heating
 them a last-ditch recovery procedure or could it be considered
 preventive maintenance? I assume that the 2120s, Travans etc.
 are prone to some of the same problems?
    
I'd say heating the tapes should NOT be done periodically.
It should be considered a last-ditch attempt at data recovery.
If you need to heat the tapes, you already know that the
chemistry is breaking down. Heating them is only an attempt
to reduce the effects, I doubt it will stop the process.