Experience points are not a reward, and should not be given out at the end of a role-playing session. A movie soundtrack is not a reward for watching nor does it come only at the end. Instead, the music is a major factor in how you enjoy each stage of the film. Proper music highlights emotions and sets the pace for scenes indicate of when characters are tense or relaxed.
Experience points can be seen as a soundtrack for your RPG - what you reward and how many you give out goes a long way towards shaping the world of your game.
In Dead and Back, there is a certain level of antagonism when it comes to the use of Advancement Points. They are a vital resource for healing and recovery of used mental stats of your character, or a means to increase the abilities of someone else. This choice gets even more difficult with the possibility of group and place AP are introduced into the mix. (further splitting the choice; heal, help the community, or strengthen your allies.)
Giving out a large number of points per session makes it possible to heal and spend on others, allowing for safety and quick advancement. Allotting only two or three points each night means fully healing could often be near impossible, much less saving up to purchase new stats for your friends.
Give out AP in the last quarter of the game, and then roleplay the choices of how to use them. Spending these points represents something going on in the world - people don't just "level up" after all. For example, the choice between improving mental stats and building the settlement is akin to hiding somewhere to read for a while, or pulling your weight digging the new canal. Does the character just sit and watch movies until the nightmares go away and their hands stop shaking - or do they get some bruises and help with their friend's jujitsu lessons? Not only can the players speak amongst themselves about how to spend the points earned each session - but they can play out the character's demands for how they should be spent or of act out the new training regimen.
Advancement Point costs are still being balanced, what ever the numbers are in the end, D&B isn't going to be a game of super characters. There will probably be a cap placed on just how much characters can improve most likely preventing more than an extra die or three being gained and maybe a few new skills. It is the players who will learn about interacting with the world, thus protecting their avatars better, rather than simple escalation of figures.