I've bite my tongue many times as well Camp Chef, as don' t want to jinks myself. I've never had an impellor failure in my life on everything from 4HP to 5.7 Litre Merc Cruisers. The old 9.8 Merc in the boat house probably has the original impellor in it and it's a 70's unit. The 2003 25HP Honda I got with the cottage was pooched though...but the orignial owner had run it out of the water to show people it ran fine (and it sure was melted). I'd suspect if you run clean, rocky lakes not such an issue. Weeds, sand etc I'm sure cuts their life short.
Problem with Muffs from say CTC...they may not cover all the water intakes letting the engine suck air while doing those laneway runs. Be sure to read the ops manual fully for water intake locations.
The other killer is all these people I see start their motors quickly on the ramp before launching. NEVER do that...get it in the water and give it time to fill the pump before firing her up.