Is replacing valve facings always necessary?

First, let me preface this question with the information that I live
in a very beneficial (or maybe benign is the correct term) climate
for leather.  Our church's 1928 pipe organ is working fine on what we
believe is the original leather chest work (it was moved from the old
church to the new church in 1964, but we show no record of chest work
being done at that time).  So I post the following question(s);

_If_ the valves are seating and sealing, do we gain anything by taking
them apart and re-leathering them?  (This is assuming the seats are in
good condition.)  The old materials are (mostly) known to be oftentimes
better than modern leather.  Also, if the pouches (given that they are
not rubberized cloth) are in good condition (here the question is more
complex), how flexible are they still?   Have the pouches reached or
are they near their maximum flexing life?  (I am assuming the pouch
leather, like other materials, has a limited amount of flexing before
failure, like most materials, i.e. metal, etc.)

I'm just wondering if sometimes we aren't making more work for
ourselves with possibly little, if none, real improvement in the final
product.

This topic came up with some loose Simplex note units that I have here.
Out of curiosity, I recovered them without working on the valves nor
pouches.  They test very well now, although I have not measured at how
low a vacuum they respond.  (I'm still a-building my "ultimate" test
bench with measured variable suction.  Real (translation: "paid") work
keeps interfering with my progress.  Okay, some "Honey-do" list items
also have priority!)

So what thoughts have you -- or have I opened Pandora's box here?

David Dewey