Or better yet, mark it when you have time to be utterly stunned and engrossed by a fic. This is sort of the equivalent of that drink in Hitchiker's guide that's like being hit in the head with a gold brick wrapped in something nice and soft. A gargleblaster? But with a less hangovery ending.
If you love Slings & Arrows, you have to read
Better a Fallen Rocket by
likethesun2. It's the story of Geoffrey's descent and recovery from madness, seen through Cheryl, who was a tech staff member at New Burbage and Geoff's partner in his independent theatre company. Also an imaginary production of an A.E. Houseman play.
I wasn't familiar with the AEH play, which adds to a nice twist to the sense of turmoil and confusion a bit, I'm sure, but this story had so much depth and breadth and beauty that I had to take two days to read it, because it can get to you in a very visceral way, like you're sliding down the rabbit hole a bit with Geoffrey. Oliver slithers through Geoff's hallucinations, which adds an extra patina of horror to what we know Geoff goes through during canon.
Although we know it comes right in the end, it's rather like, I suppose, having the full weight of Geoffrey's presence and intellect and focus directed right at you; inebriating and exhilarating and a wee bit scary. You want to sit down and rest a bit, but are unable to, because he might do one of those wonderful things that just takes your breath away.
So, put on a metaphorical helmet, gird your loins, and go read this. It's, if you didn't get it the first time, amazing.