Ben Jackson wrote:

Anybody know how for long the electric fuel-pump
in a fuel-injected Piper-Arrow IV can be
operated for.?
indefinitely ? or intermitantly ?

All I know for sure is that the one in my plane (PA-24 Comanche) is
shockingly expensive so I only have it on for takeoff, tank changes,
approaches and landing.

Like many things in aviation g

So., any views on how long the electric fuel
pump can/should be run for ?

Besides wearing it out you should also look at a fuel system diagram and
see how it works. Early Comanches pumped around the engine pump, leading
the engine driven pump to overheat and possibly vapor lock when you
switch the electric pump off after a long use. Later ones pump through
the engine driven pump and avoid that problem.

The arrow (from what I can deduce from the one-page diagram) has
a 'through the engine-driven pump' system.