50% down on a position is my line in the sand. More than that, and losses may be accellerating rendering the position meaningless, though some stocks recover from that as well with good margin. It is good to use tricks to reduce drawdowns further of course, so this is just one of many factors to account for and not a major one at that, since it's detached from historical PA. Most other SL will kick in way before this one.
I see 0.5% and below as noise/spread, while 1-2% start to becoming movements with some meaning.
Of course, depends on timeframe, market, leverage, and strategy, but this is typical for long-term stocks in my experience.