hi,
my workaround just now is to use ExtendLock, available from Marketplace.
it's a little inconsistent, and doesn't seem to work at all if you set it to a week (not on mine anyway), but i have mine set to 24 hours and it mostly only asks me for the password a couple of times a day (sometimes it's more! it seems a bit random!), which is certainly an improvement on the "every 10 minutes" setting my work insists on.
hope that helps