I think there are a number of factors that come into play the most significant 1. Line lengths you practice at. 2. Age 3. Physical Condition. 4. Number of passes For me at 69 years old, in what I consider good physical condition, I typically need a day of rest between skiing day, usually one sometimes two sets. Shorter line pass take a greater toll, if I ran 28s and 32s, I could ski every day. 32, 35, 38, 39, 39, 39, 38 or 32, 35, 38, 38, 39, 39, 39, 38 are typical sets. I am pretty much gassed when I am done, and more often than not do not run a 2nd set.