My approach:
Session 0: Tell all the players to roll a backup character, tell them that character will likely die horribly and make two more. Usually after telling them that they ought to have at least 6 backup characters they get the picture that they should usually have one. I allow them to keep that character "AvPL -2" so that when they bring them in they'll be behind, but not so far as to risk getting squashed once again.
Session 45: Bob died. We are sad. But Bob WAS NOT PREPARED! and did not bring his backup character. Bob may make a new character while the party continues on, or run some minor NPC (if available) during the game, but otherwise Bob sits out until his new character is done. The DM then wiggles his fingers and NuBob shows up, a straggler from another adventuring party, some poor sap suckered into the woods by faeries or whatever. I'll usually attach a quest to NuBob to help give the party a reason to let him join.
Session 66: Joe died. Joe had his backup Jim ready. The party encounters Jim somewhere along the road and Jim joins the party, yay!
So yes, I tell my players to be prepared, or be prepared to sit out the session until they have made a new character. The group may choose to keep playing, take a break or whatever, I'll leave the call up to them, they may think now's a good time to grab some pizza or just to stop for the night. But if they want to and I'm ready the party rolls on.
Sometimes we have funerals if it's a reasonable possibility to take the body back to a town and give it a proper burial. PCs that don't just die day one from landing on a pointy stick deserve to be remembered.
We have one guy in our party who is dying almost every other session. I don't know if its bad luck or he's just being stupid or what at this point, but he dutifully rolls up a new character each and every time, so....okay man.