Usually every time i fly, which isn't much at the moment as i'm sure many others know only too well at this time of year!
Having said that i don't go below 500 ft in a PFL on too many occasions, re. the point about possibly being nicked for low flying, however we do have the use of a rather large stretch of beach about 5mins flying time from our club....
Cue PFL's to the deck, often with the fan stopped...
It's quite a difference in gliding performance when you're dead stick, and though you don't have the same demands on field selection ( borders, surface, slope, crop ) by picking a point or offset feature to denote the start of your " field " it can be very useful practice.
Plus it gets the heart rate up a notch as well!
WBV