Chemistry major here so I always had lab in the afternoon, then it was lab and research for my senior year. I spent a lot of time outside of class/lab studying, chemistry homework, writing lab reports, getting tutored on calc, going to office hours for more calc help, so lots of time not skating.
However, I prioritized skating as much as I could while maintaining good enough grades to keep my scholarship and to graduate on time. I always made time for skating even just for an hour. I'd immediately go push around campus after lab, I had to. I skated as much as I could throughout college because I needed it. I got burnt out on lab work at the end of my senior year, partly because I couldn't skate as much. I knew I didn't want to go to grad school, because it would mean less skating, among other reasons. Try to find the right balance of getting in as much skating as you need, but also keep up with the schoolwork, it's not impossible.