Hi
If you do every thing right then thay shoud last as long at the boat.
i.e Servicing every 100 hours or so, winterizing, dont do any thing stupid with them,check the oil on then every now and then, new impeller every 150 hours ( we do it bit ott but hay), check anodes every 50 hours and bit of grease in the right places.
If i have missed and thing out outher people will soon put me right.