I, too, switched to leather a good number of years ago after a pump
I recovered in cloth had holes in the corners within one year!  I have
recovered [with leather] four Welte rotary box pumps, an Art Echo and
Duo-Art pump and all are still performing well with no holes.  I
recently re-inspected the pump on my Steinway Welte and there was no
sign of wear at all.  This pump was recovered about eight years ago.

I used leather from Columbia Organ Leather and have been very happy
with the performance. I did seal the leather but it is otherwise as
purchased.

Mark Reinhart
Charles Town, West Virginia