It depends on what height I'm working, A long row of windows over 30ft, I take a bit of a break after doing about six of them, I don't mean stop working, I just do the first floor windows with a lighter pole.
I can use a standard Harris pole all day without aching, I am aching right now though, I stepped back to pull my hose off a fastner and forgot about the step behind me, I ended up flat on my back, hence the ache.
I'm a right old git 66.