For me, four hours a week is sufficient to stay up-to-date on an active research area but making forward progress requires at least twice that.
> You are awake for at least 16 hours of the day, you telling me you cant find 4 hours a week to read a paper? So 4/112 hours or around 3.5% of your week...
Using awake hours as the denominator is misleading because most people have other non-discretionary time commitments besides sleep. For me I'd estimate ~60h/wk sleep, ~50h/wk work/commute, ~30h/wk non-discretionary upkeep of children/relationships/home/body. Assuming 8+h/wk to make progress out of the remaining ~28h/wk of discretionary time means I can handle about three non-discretionary priorities. (Pre-kids I could handle about five.)
Therefore, when someone with a job says "I don't have time" to pick up a hobby, skill, language, outside research area, instrument, volunteer position, etc I don't interpret their statement as meaning it is physically impossible for them to rearrange their schedule to accommodate it. I (and I suspect most people) interpret the statement as them admitting that it's not one of their ~3-5 non-discretionary priorities.