Kneepads pretty much all the time, there’s so little reason not to imo. Good quality and good fit pads are barely noticable once on, til you fall off anyway. Wore my 661 Rages to solo the glentress seven frinstance, no bother. The thing is it doesn’t take much to upset a knee, I bumped mine pretty gently off a shifter in a really low speed dismount, not even a crash, and couldn’t ride for a fortnight, really annoying. They’ve probably never saved me a big injury but they keep me riding and save a lot of hassle and irritation etc, totally worth it. Honestly in terms of the amount of knocks, my knees take more dings than my head so there’s probably as good a case for pads as for hats.
Elbow pads often, but there’s more drawbacks to elbows I find, mostly this is about heat- I have a great set of POC hard elbows but they’re very bulky and full-on, and a nice set of Gform low profiles but they’re still pretty warm. TBF most elbow pads seem to be rubbish, I suppose they have a harder job to do
Wee bit of stream of thought… I don’t really get the thin kneepads thing, bulk isn’t really a problem on knees unless you want to wear them under trousers, so why lose protection? Side protection’s really useful and most of these have none. They don’t tend to be any cooler either and sometimes they’re more restrictive (because getting the same protection into a smaller piece needs more complex armour pads)
Sometimes I do the “pads on for the hard bit” thing but frankly there’s no guarantee that’s when you fall off! I fell off in a fireroad ditch on skyline the other day, pulling over to let a truck past, and absolutely clattered myself- pure luck I had them on and really glad. I think the ideal is stuff you can wear all the time because I reckon if you wear pads 95% of the time then there’s a 95% chance you fall off in the 5% you don’t.