Yeah, my group just hit 24, and the Archlich has already started joking about how the best way to get him back in the fight will be to kill him. (Given the group is pretty much all strikers, with one defender and no leader, it could well happen...)
As it is, I've been trying to boost the difficulty / lethality a bit as we've been approaching this point, in anticipation of people gaining such powers. The Archlich ended up being the only actual personal 'don't die' power, compared to several that prevent dropping at 0 - but the defender got the power to die in someone else's place (and then come back to life), which pretty much covers the whole group.
As it is, I've been trying to boost the difficulty / lethality a bit as we've been approaching this point, in anticipation of people gaining such powers. The Archlich ended up being the only actual personal 'don't die' power, compared to several that prevent dropping at 0 - but the defender got the power to die in someone else's place (and then come back to life), which pretty much covers the whole group.