Hey guys. I'm a big fan of the way EXP is handled on 2E, and I have no intention of abandoning it in favor of milestones (though I'd do it if I had to).
The thing is, as I'm nearing the end of book 5, it occurs to me that there is WAY too much EXP on this book and the beginning of the next.
Now, the book is vague enough with the milestone suggestions. "The PCs should be level x before y." That's the usual format, which is very much open to interpretations. The thing is, for example, if I track EXP correctly, my PCs would reach level 18 on the way to fight the book 5 boss, for example. I'm aware of the fact that there should be some extra EXP because many groups will miss parts of it, but a huge chunk of the adventure is unmissable, so it's pretty impossible to not be overleveled pretty early on, I think.
How have you guys dealt with that, particularly on the last two books? (I hadn't felt this with any book all the way up to book 4).
I wouldn't worry about it to much. Sometimes your players will be higher level then they are suppose to be, sometimes they will be lower. At the end of the day, it all balances out. If they hit level 18 and are doing content meant for level 17's, the XP they get is less because the difference in level.
For example, the fight you are talking about is normally 120xp (1 equal level and one +2 enemy). But if they are level 18, now that fight is only worth 90xp (A -1 enemy and a +1 enemy).
It does make the fight a little easier, but not so easy that it will ruin the game. There were a couple points where my players were up a level ahead of time. It didn't ruin anything on my end, everyone still enjoyed the fights.
APs are designed to have more XP than you need, because the expectation is that only 80% of stuff will be encountered, I think. So like there is always more treasure, and more XP than you need, with the expectation that the palyers will organically bump into around 80% and hit the level and gold benchmarks at around the right times.