When I was unemployed I used to walk waaaay more than I do now - both to get to places and just as a hobby - and I’d hope to do the same when retired, as long as I am fit enough. That’s walking though. Standing in one place is something that I find extremely wearing and have never done when not necessary. As I understand it this is fundamental to the nature of bipeds. To stand still, we constantly need to adjust balance. However, when walking, it is basically a continuous, controlled fall forwards, and takes less energy. For quadrupeds, it is the other way around: they are stable when standing, but require constant effort to walk or run.
I probably spend most of my reading time horizontal rather than sitting, but if I am reading when vertical then, again, it will be walking - or pacing around - rather than standing. I would seem really weird to simply stand there and read.