Experience points, encounters, levels, there’s a lot of ‘lego mathematics’ in 4e. You plug in such and such encounter and that entails such and such reward and such and such experience points. If you stick to that in planning the long-game then you’re either limited in how far ahead you can plan or how much latitude you can give your players. Given that it’s also a game of heavy prep (though less than previous incarnations of D&D perhaps) this has knock on problems that can encourage railroading.
There’s various routes you can take to be more fast and loose with the XP/Level/Reward system, you can wing it, award XP per session, level at intervals, but – frankly – bean counting is, I think, a massive part of the reward cycle in D&D type games. Gaining a level should be earned and should be felt to be earned. That said, some of the things I want to emulate are CRPGs which means I want to include ‘side quests’ and ‘character quests’. Things that are beyond and outside the main plotline. I also want the players to be able to wander off the beaten track in a semi-sandbox fashion.
The main plotline will be what earns the guys their experience points but for things that go ‘off the rails’ they’ll earn ‘Karma points’, these will be earned as if they were XP but will be tradable – at a rate I haven’t yet decided – for access to benefits, contacts, making items that aren’t normally available, available, personal plot stuff and so forth.
That’ll also allow us to extend sessions at a particular level of play without me having to do a ton of extra prep work. I can re-use beasties and bandits more often and get more use out of the same work while still allowing the players to get their reward kicks.