JacquiS My arm movement wasn't significantly impacted for long. I was brushing my teeth again with my affected side after a few days, driving the car four days following my sentinel node biopsy and a week and a half after my axillary dissection.
I took the surgeon's advice about not trying to do things above shoulder height at first. I found it quite easy to tell how much movement my arm wanted and not over-doing it.
The complicating thing was anything that required pushing or pulling (opening a fridge door, using cutlery, using a stapler at work) my arm didn't have the strength at first but I made do with my non-dominant side until my dominant side was ready. Everything was do-able.
The exercises are really helpful not only for the muscles but the mind as well as you will notice improvements as you regain movement.