It’s okay. I used to think I don’t have much time, but that’s not true - despite being busy working, I can do reviews without problem. In the train during commute, for example, I can hammer out like 100, which then takes roughly 40 minutes (because I’m slow on my phone), but that’s fine - nothing else worth doing while sitting (or standing) there anyway.
I think my limit of doability would be closer to 400-500, but I probably won’t keep that up, so if it gets too much, I’ll just stop doing new lessons and work on reducing the pile for a month or so.
Regarding reorder script: Almost everyone, including myself, seems to do them in the order radicals -> kanji -> vocab. Maybe it would be smarter to do vocab first, because it still belongs to the level before, and in the grand scheme of things, one hour delay should still not make a big difference.
The reason I think doing vocab first is, it puts you in flashcard mode, you’re already in the flow at the point when radicals and kanji come up. On the other hand, your brain is still fresh at the start of a session, so you might want to take a break after the vocab.
Maybe it balances out by itself.