When is it a good time to resign?

This has changed for me a number of times over the years.
Recently, I've tried to fight on for as long as possible, and I only resign when the opponent's winning plan is obvious, and I can't do anything about it.
I'm interested to know what others' opinions are in terms of whether it is better to resign as soon as they start losing the game, or fight to the death?

For me more than a piece.. as long as I can't see any counterplay.

Counter play is the key.
The only important thing in chess is mating your opponents king.
There's lots of examples of players being lot's of material down and still winning the game.
As in the above post, I only resign when defeat is unavoidable or I can't see any useful way to progress which could lead to a mate

My question is: 'Could I win this game playing my opponent's position?' If the answer is 'yes'. then I shift into my 'go for the draw mode'.
That mainly consists of throwing away anything if I can end up with a perpetual check (3 fold), usually with my Queen. It has worked enough since people don't expect a non-attack sacrifice.

Originally posted by @sigmund-freud
This has changed for me a number of times over the years.
Recently, I've tried to fight on for as long as possible, and I only resign when the opponent's winning plan is obvious, and I can't do anything about it.
I'm interested to know what others' opinions are in terms of whether it is better to resign as soon as they start losing the game, or fight to the death?

I will usually play on in a lost game if I think I can at least make things complicated. Plus, I pull off swindles sometimes. [I also occasionally give some away.]