Originally Posted by VinoD
How long can I leave it sit in a, basically, stalled state before I have to add potassium sorbate and sulfite?
First of all, it's not in a stalled state. You don't know that it won't ferment lower, and you can check it whenever you want. Most people don't worry about it, and just check it "later". When the wine is crystal clear, and you rack it to another carboy to get it off the lees is a good time to check the SG.
I let my wines sit in a carboy for a long time. I have a rhubarb wine in a carboy that I made in May of 2008. It's clear, and it's finished, but it's fine where it is until I bottle it. Since I'm not sweetening it, I won't be adding sorbate. I do use sulfite at every other racking, though. Usually, I use one crushed campden tablet per gallon at every other racking, which keeps the sulfites in a good range to help preserve the wine and help prevent oxidation during racking.
I'd let the wine sit now, and see if the SG drops. If you get some thick lees, you can rack it whenever it needs it but you can wait 30-45 days at least between rackings.