if a regular player plays against you, then your bluff is not needed at all If you play against an active player and an aggressive player, then don't use a bluff, it's better to bluff against a passive player or fish
I usually find myself in that awkward situation where I know my bluff is not working, and just give up in the turn, hoping the villain bets so I can fold, and save myself from the shame 😅
If my hand does not improve at all I may check the turn. But if I picked up a flush draw or paired a card or picked up a straight draw I am still betting. What I do on the river depends on the cards that come and what I suspect my opponent has. If I know he paired a card and he is not going anywhere then it makes no sense committing more chips. If however I suspect he has nothing but an inside draw or flush draw, and I know I can only win the hand by betting the river than I will, but it's important not to overbet.
I think it depends, I think your question is a little incomplete because you don't say if you are the hand's aggressor or if you are the hand's defender so that has to be taken into account, but I think you have to give up the semi-bluff when you realize that the villain won't give up
"It's better to run with a good hand than to lose with a great hand"