Should I be skating with a rigid ankle? The boots are obviously designed to flex a bit, so presumably this is ok. I have got a lot stronger and faster in the last couple of years, and am presumably pushing off much more firmly than in the past, which is probably why the problem has arisen now, if it is not simply the material decaing
I have K2 Moto 100's - I noticed that after skating, my ankles were sore, and that while skating, the soft boot felt like it wasn't supporting the ankle fully. I tightened the cuffs as much as I could, but I still felt strain/pain either after 10+ miles while skating, or afterwards. I don't think the 100mm/90mm wheels help - the taller wheels clearly exacerbate the less-than-ideal support. They're fine for medium distances, providing I don't try to get too far over on the edges when pushing.
Saying that, I've had to stay off inlines altogether as my ankles were getting trashed. I've stuck with low-cut speed/roller derby style quad skates for a few months now and my ankles are WAY better. I had to sell many pairs of Seba and Rollerblade hard-shelled skates over the last couple of years due to ankle issues. At times I couldn't walk on one or the other ankle. Thankfully I can still skate now, but I do miss inlines...I did manage to get 22.6mph on a downhill stretch on my quad skates; not bad with 64mm wheels, lol