Roughly speaking domestics are good for 500 to 1000 hours
Commercials good for round 2000 + hours
As already posted, flat level ground & proper use can increase this
Keeping the cases clean, particularly the left side also helps
Towing heavy loads up hill & running the engine slow can drastically reduce it .
Changing the oil at around 200 hour intervals can help as well but no much with your mower as it has external brakes .