i have a problem caching workunits...

i am only crunching seti.
my workstation is a 2 x 2,2 GHz Xeon with an optimized client.
1 workunit takes about 1:25 to 1:30 to finish.

my preferences are:
Connect to network about every : 4 days

but caching is only about half a day.
if i raise to 10 days, then caching is about 1 day.
if i finish a wu the client is requesting only a few seconds new work
(to 20-30sec)
if seti is offline for more than 1 day i am running out of wu.
sometimes boinc is saying that my pc is overcommited, but i am only
crunching seti and nothing else.

i am running several pc and none of them have problems to cache 4
days.

is the only solution to uninstall the client and reinstall and
reconnect to seti??

i am frustrated about this because it seems i am the only one with
this problem. at google i only can find problems with several projects
(overcommited) but this is not the same like my problem.

any help?

regards
alonzo