Changing my P1s cleats
I change cleats when they're worn to the point of a corner/ledge is missing chunks. 

At this level of wear, the cleat can unclip easily and sometimes spontaneously.  In this state I can still ride, though not as aggressively on take-off or high power.

If you have an event coming up, like a race, a long ride, a group ride, or similar, then change your cleats before they get to the "pieces missing" stage.  Do get at least one test ride in before your event to make sure the new cleats are positioned well.



For your photo, I would call the cleats MARGINAL .  Certainly change those for an event this weekend, but if you're just commuting then there's a month or two left in them.

I guess you're a left-foot down rider (like me), cos the shoe on the right of the photo seems to have more wear than the other.  I always save my worn cleats, sometimes getting months more wear out of two former-right-foot cleats.  A pair of utterly-knackered cleats make for great inserts so you can ride the bike in flat shoes too.  Good for a shopping trip.



Do notice that cleat wear is almost exclusively from walking about in your shoes.  There is almost no wear imparted from riding, other than putting your foot down at a red light or stop.

Cleat wear can be minimised by not walking on concrete, and by avoiding spin-turns on the ball of your feet when walking.  You can get cleat covers, but they're easily lost and still hard to walk in.

I sometimes wonder if aluminium cleats would be practical.