Hemoraging rear main seal - what to expect??

Alrighty - my brand new rear main seal is deterorating baddly. I suspect the truck will bleed to death before the end of the month. In the meantime, since this is un-repairable and I don't have the time/finaces to get new motor yet (and I must drive this until I get my mustang back) what can I do to prolong terminal damage? What do I need to look for to tell when the damage has reached its limit?