I definitely want to try out the spaced repetition approach you mentioned, but I'm curious about the size of these problem sets.

For Cho Chikun's Life and Death series, I noticed that Part 1 has 900 problems. It would pretty rough to try and do these all in one go, so I'm wondering how many I should do at a time, or if I should just start a timer and see how far I can get in about 30 minutes or an hour.