I haven't used silicone rubber tubing in an instrument, but I have
lots of experience in the lab with various tubing.  We use a variety
of Tygon, rubber, and silicone tubing around the lab for a whole
range of uses.  The choice seems to be based on tradition, cost,
and occasionally appropriateness to the use.

Because of the chemical and sometimes mechanical stresses, it might
be thought of as an accelerated aging environment.  Rubber tubing
generally has a very short lifetime, typically months, seldom over
a year.  Typically it fails by becoming hard, brittle, and developing
cracks.  Tygon can last much longer, it splits when bent repeatedly,
and eventually turns yellow and gets slimy.

Silicone rubber tubing lasts forever as far as I can tell, but it costs
a relative arm and a leg.  It can work for many months in a peristaltic
pump where it is constantly flexed.  A downside in piano work might be
that it is very floppy -- it won't stay where you put it.  It needs
a thicker wall to not collapse under vacuum, so there may well be
issues of fitting things in.  I would be pretty confident of longevity
though.

Cheers,
Roger Wiegand
Wayland, Massachusetts, USA
www.carouselorgan.com