My group gets awarded xp at the end of each session based on their level adjusted a little for how well they played. The base amount is one fifth of the required xp for the highest level character to go up a level (i.e. new level min xp requirement minus current level min xp requirement divided by 5.) If they stuffed around all session they may only get one tenth. If they complete a major component of the campaign a quarter or a third.
This means:
a) they are not focused on combat unless it is required for survival or to achieve an in-game goal. They will hunker down to achieve goals rather than trying to find things to kill.
b) they still have xp for creating magic items, powering spells, etc
c) lower level characters can still gain ground on the higher level ones in regards to levelling
d) Less admin. I don't have to calculate xp from combat