Hiya!
What I did was this:
When you die and get raised/resurrected/brought-back-to-life, you immediately make a "death save" (10<, fail, as normal). If you fail this, you fill in one of your Death Circles...permanently. This means you only have two "fails" left if dropped to 0 or lower. If you die again, and get brought back, do it again; make a Death Save. Fail = fill in your second Death Circle...permanently. Now, every time you die and get brought back to life, there's a 50/50 chance it just doesn't work. If you fail that Death Save, fill in the final Death Circle. Your character is no longer able to be raised from the dead by any means. His soul is too weak with this world (or to strong with the other...).
So, while this doesn't really 'stop' the treadmill of characters dieing, then being raised the next day (or round!), eventually the characters luck will run out and it won't matter. Dead is dead.
ALTERNATIVELY: You could make a newly raised character make an immediate trio of 'death saves'...as if they were dieing again. No help will work (no magic, no Medicine check, Healers Kit, etc...just flat d20 rolls). The player rolls d20's until he gets 3 successes or 3 failures...whatever happens first...that result is his Final Result. In other words, if he rolls 11, 8, 9, 14, 3...he failed 3 times before succeeding 3 times. The character is DEAD. Does not come back to life and can NEVER be raised/returned again. Perma-death. If you REALLY wnat to be serious, have each dead automatically perma-fill a circle. So each character simply has 3 "ressurections"; with three filled in Death Circles, the next time the character hits 0hp or lower, they are just dead. Period.
^_^
Paul L. Ming