[W126 Coupe] rear hydraulic suspension pump duty cycle

[flakeymail-benz at yahoo.com]

howdy,

how often should that pump be running, and for how
long?  my 560 coupe is new to me, and i'm noticing
that little pump seems to be running a lot, with the
car parked, idling, and a steady load in the trunk. 
it'll run for at least 5 minutes w/o shutting off.
shouldn't it build up to pressure and cycle off
quicker than that?

it seems to be holding its oil fine though, no
apparent leaks.  

suspension rides ok, a little "thwacky" from the rear
over bumps, but no outrageous misbehaving.

cheers,
alex