The longest stretch

What is the longest suggested duration of a stretch? I was thinking - could a long upward stretch (for example, while sitting and watching TV) be a good substitute for OTS hanging? If not, why?

Nemanja -

“If not, why?”

Because hanging weight affords you a constant stress that manual stretching can not. The objective in hanging is to apply static tension - letting gravity do the work instead of the more erratic stress levels the hand can offer.
At the end of a 15 minute set 10lbs is still 10lbs, and the tissues you seek to deform would concur.