To respond to your question about archival storage of storage pool
tapes:

It is unwise to put a data tape away for years and never read it.
It can happen with *some* tape that the long-term proximity of the
  winds can cause "print through" as the magnetization on one wind
  can induce a ghost image copy of that pattern on the adjacent,
  contacting wind.  (It is a historic problem with audio tape.)
A tape never used is a tape whose condition is an unknown:
  Unless you rotationally use your tapes (as ADSM tends to), you just
  don't know how usable a tape is.  Also, a tape stored away for years
  tends to become a tape forgotten.  There are countless stories in
  data processing of vital, archival tapes getting lost or deteriorated
  over time due to moisture, mold, mishandling, etc.
Things change while the tape is frozen in time:  While the tape is
  stored away somewhere, the software that originally created it is
  going through PTF, release, and version changes.  The hardware that
  wrote it is going through microcode and drive tolerance changes.
  Such factors contribute to various degrees of incompatibility which
  increase over time.  There is good probability that hardware five
  years from now may read today's tape, but I would not count on that
  future software being able to fully interpret it.
Commercial media is intended to be transient, not archival:
  Common technology is not designed to last for long periods - not to
  cheat the customer, but simply because of economics and that the
  advances in technology cause us to move on anyway.  Tapes are almost
  totally plastic, which inherently gets brittle over time as its
  polymers dry out, which also causes it to change dimensionally, which
  thus stresses the oxide coating.  By rotationally using and thus
  copying the digital data on tapes we both assure that it's readable
  and mitigate the aging effects on the minute magnetic domains on the
  tape by "renewing" them in regeneration on another surface.

So, your best means of assuring the quality of your media and data
thereon is to keep it circulating.
     Richard Sims, Boston University OIT