I've been down to agree to stuff as much as like three months in advance, and sometimes I've come through. But it's not ideal for me to make those promises, because I am a flake. Last year I agreed to do stuff with people (who were so excited about it because COVID was "over") a month before it was supposed to happen and I had to flake on them all because I needed to go to a CSU so I wouldn't die. When I left I didn't really feel up to going on a road trip, which everyone was very understanding about because if I'd died before the trip took place I wouldn't have been going anyway, but I just still felt bad. I think a week or two before at the most is the best way to go.