I have a 20 hp kohler command, 1700 hrs, still going strong.
I think the key to long engine life is change the oil, filter every 60-75 hrs, when oil turns dark on dipstick.
I run all my engines about 80%, never full speed. I had a new briggs that use oil when it was ran at 100%. Slowed it down and stopped oil consumption.
Check oil before you start it. Seen too many rods out the side of engine because lazy people didn't check oil.
MICE AND GRASS CLIPPINGS. Take the cover off engine and make sure a mouse hasn't made a nest over the cooling fins or grass isn't blocking the cooling. Seen too many engines with low hours die from a mouse nest or grass clippings.
54 inch and 4 acres means you like to sit on a mower longer than I do. When I was younger and couldn't afford a bigger mower I pulled (3)21 inch push mowers behind my mower. Yes, it looked funny, got people stopping to see it. My kids refused to mow unless the push mowers were hooked up and working. Think about it, golf courses use gang mowers, why do you? Gang mowers follow the uneven lawn and does a bang up job. Try it.
I have a 48 inch Husqavarna, briggs 350 hrs. Use as a trim mover. Have a 48 inch JD gt275, Kawasaki, no hour meter, 19 years old, trim mover. Jubilee 72 inch woods and Farmall C 72 inch woods, main mowers. Each cut over 4 acres.
Pic of what yard looked like after recently cutting it with Farmall C. It takes the JD gt275 30 minutes to trim around all the flower beds and buildings. 40 minutes for Farmall to cut just the yard. More grass if you count road side and gravel pit. Get your pto fixed. geo