Wow thanks for all the replies. The bindings thing sounded really promising but it sounds like some of you have had my exact problem and found out that it was the boots, so now I'm not sure what to do.
Lisevolution you mentioned that it was the muscle next to your shin that was aching - I'm wondering if you mean the tibialis anterior and not the peroneals. I know it seems like splitting hairs but the tibialis anterior would get tired if you felt the need to dorsiflex your foot constantly for stability, but the peroneals get tired if you're constantly everting your foot. This is why I thought the canted bindings might help since it seems to address the issue from a medial/lateral perspective rather than an anterior/posterior perspective.
The thing is I actually really like my boots. They're super snug but not so tight that they interfere with circulation. My big toe goes right to the end but just barely - so that my toes don't ache at the end of the day. And my heels don't ride up. So I can't imagine having boots that fit me better, though maybe that's not what you're saying...? Maybe it's the stiffness of the boot that's the problem?
My ultimate solution, plus the right boots, was moving the ankle strap DOWN, lower, on the bindings. Burton's are easy t move, some brands don't have the option, Union you can make the heel cup smaller. I think it allowed my ankle to flex more naturally.
I had the exact same symptoms, lead leg.
I never tried canting.
If you know your boots are good, don't worry about that variable.
Also, don't work out too much while in season. too much repair while in the cold is not good. I work hard on my ankles in the off season and it has paid off. PLus, I skateboard indoors everyday.