SPDs- never, because by the time they need replacing there's no way I'll be able to get the bastards off.
Well, I had to do it.
I've had this twinge in my left foot for a couple of months and it seems to be getting worse. On the way to work this week I felt that my left foot was a bit too far forward on the pedal and I wondered if that was what was doing it. So I've moved the cleat back a bit.
First they were pretty rusty (salted roads and rain). I had to scrape out the hex heads with one of those mini screwdrivers. Plusgas over the cleat bolts. Found a good Allen key that had hardly been used and got the long end nicely engaged, then used an adjustable spanner on the short bit for leverage.
Took a few goes but I got them all loose (I did the right shoe too- I didn't move the cleat but I thought perhaps loosening and re-tightening the bolts might help if I need to change it in future)
I did install them with a bit of antiseize grease originally.