I have Speedplay Frogs on all my bikes, and I try (<< that's the operative word!) to follow the manufacturer's recomendation for routine maintenance:

- once a week (which for me is ~100-200 miles) I lube the cleats and cleat contacts with a dry Teflon-based lubricant. (I use the Finish Line stuff in the red bottle.)

- once every ~2,000 miles I grease the axle mechanism with a grease gun and standard waterproof grease via the access ports on the ends of the Speedplays. Keep squirting grease into the port while spinning the pedal until old dirty grease oozes out the opposite side around the spindle.

My oldest pair of Frogs is over 5 years old and has maybe 20,000 miles on them; they show no indication that I can't get several more years use out of them, so regular maintenance seems like a good -- and relatively cheap -- idea.