Mouse,

This is something I've been trying to figure out for the past 3 years. Everything that I have read, been advised upon, and more importantly tried on myself is "let thy body tell you when you are pushing to hard, and reduce intensity, exercise time, or both"

I'd say keep track of what you can do, and notice how and what causes you symptoms. Stay below that threshold for now, and every once in a while, extent time/intensity for a bit to see of the headache threshold is there or if some recovery is noticed. However you want to keep track of it, time, duration, heart rate, type of exercise.

I can really understand what you are experiencing with wanting to exercise but can't because of headaches. I thought my body and brain were going to simply be able to jump back into my typical routine of running 40+ mile weeks & training for triathlons. Nope. I was only able to muster walking for a short time, then was able to race walk without getting exertional migraines.

For me, early in recovery, headaches and PCS symptoms (cognitive fog mostly) happened within an hour or two, and now, sometimes it takes a day or longer. Swimming headaches used to cause a headache lasting 24 hours and road cycling for 90 minutes used to give me a headache lasting several days. This past week I did some swimming and didn't get but a sliver of a headache.

It doesn't take much to keep the body healthy, find what you can do and do as much as you can!

Good luck to you.

Mike