I'm with Iserith, In my game no attendance= no XP. My game has a spread of about 5 levels between the most frequently attending players' characters & replacement characters for those who died. Those who attend less frequently (due to real life issues like...work) are now 2-3 levels behind the highest level pcs and it hasn't really been a problem.
I don't really get this modern "it's not fun if we aren't all the same level" type of attitude. You earn xp by being present at a session in my games (whether by slaying monsters or stealing their stuff, or my typical by getting a preset amount of xp per session no matter what happens). If you can't make it for whatever reason then tough. It is also not fun sometimes for the rest of the players to be expecting to utilise your pcs skills one week and you aren't there but we accept other things real life events/commitments intrude on game night, shrug and deal with it.
But that being said, the player most effected by crappy work hours doesn't complain about not being the same level as the highest level pc. He simply gets on with the game, rolls his dice, enjoys being present, contributes to the story/game and is not underwhelming or overshadowed by the higher level pcs by any stretch of the imagination- which is one of the strengths of 5e.
Stormdale