SPD-SL cleats usually last me a full season without using cleat covers for walking. I don't walk in them much though and they do wear pretty quickly if you do. But those wear photos are pretty extreme!
SPD-SL pedals are excellent though, despite the walking limitation. None of the other road systems are any better for walking (Look, Time, Speedplay). In fact Shimano is probably the best for limited walking ability. Yeah, you could move to regular SPD for much better walking ability. But I find my road shoes so much better on my road bike that I would never entertain that route myself.