As everyone says, there is no right or wrong, it's what works best for you. Like Cate, I worked through treatment, found it really beneficial but then again I was able to do so (no nausea, no fatigue). I did have other side effects but they did not stop me working. Staff and Director were all very supportive.
I cut back one day after about a year, not because of cancer treatment but because cancer forced me to accept I wasn't getting any younger (I was 68) and my work/life balance was terrible. I do a busy 4 day week, find that works really well for me, and have more time for other pursuits ( have finally joined a local choir, and the gym). Good luck with whatever you decide.