Interesting, we have very few problems with leaks. Or water pumps. Or hoses.
Been using L\C mowers since '79 when we bought our first Toro Groundsmaster 72 with a 19 HP Continental. Sold that one with over 4,000 hours on it, had over 6,000 last I heard. The other 2 we had both had over 4,000 before our first major engine problem. Otherwise normal tuneups and oil changes. Never had a water pump on those.
2 Toro 455D's, 1 Toro 4000D, a Howard Price 1260, Toro 3000-D, Exmark Lazer all had L\C since then. Coolant and leaks were never a major problem on any of them. Hard to say the cooling system was even a minor problem on any of them.