I had to wait until I healed up from surgery, which took a little over 3 weeks at my age (mid 40's). The radiation oncologist started setting everything up (targeting, mask forming, trial runs) after 2 weeks, though.
I had treatment once each day, and it consisted of getting positioned on the table, getting the mask locked down, and the radiation doses.
I got one 15 second shot on the left, one on the right, and a 30 second shot from the front. I was in there there less than 5 minutes total.
73 O-O