I have four campaigns I'm involved with - one is a homebrew I run, and there is no story hour with that because I am not a player.
One is of Hawaiian flavor, and that one alternates with another one that is in cauldron (with Cordozo the lawyer). But I've not written on either of those in a while because both are on hold while those two DMs (a couple) take a break.
And so on that break we started another group, where I'm working toward the True Necromancer prestige class (Vincent's Lab Notes). That is eventually going to be run by the two players in our group who have never DMd before, but I said I'd run it until everyone was up to 5th level or so, so I've been runing Vincent as an NPC and taking them through Sunless Citadel and Forge of Fury (which I ran when they first came out years ago... and these players never have been through).
It is hard to do writeups when your character is an NPC, at least the way I do them - I don't have time to make many notes and I have to pay attention to far more than just my character, so it is somewhat abbreviated. But that will change when I'm not DMing.
I always try to keep up with my writeups. Generally, I always get my write up for a session done before the next session starts. Sometimes that means doing it the next morning, sometimes that means doing it the afternoon before the next session. I like to do it earlier rather than later, so I don't feel rushed. Sometimes I work on it over a week. I take notes and try to stick to the highlights when it comes to extended dialogue or combat.
Given my busy schedule (and busier 16 month old daughter) if I don't keep up after each session, I'd fall behind and never catch up. So I always stay current. Sometimes that means I don't get as much writing in as I want to in a write up, and sometimes I miss small things, or don't get it quite the way I'd ideally want it, but at least it keeps me current.