I have seen a lot of mowers come in. Usually, they have never had an oil change. Most of them are borderline worn out by the time something serious goes wrong. Serious means something costing about 1/4 of a new mower price. They usually have 1000 to 5000 hrs. on them. So, there is no realistic way to say how many hrs. a mower should last.
Any mower has to have certain preventative maintenance done on them to keep them running as long as possible.
Some preventive maintenance is as follows.
1. Oil change at least at the beginning of mowing season. Depending on if it is used to cut just one yard or several yards.
2. Grease all steering, deck, and axle fittings.
3. Remove engine top cover and blow out start of each season.
4. Note any rust and use either sand blaster or antirust chemical to remove rust clean and paint.
5. Check, sharpen or replace blades every 8 to 10 uses for normal yards. But this depends on how rough the area your cutting is. Normal yards are level and have very few things that the blades hit but a rough yard there may be many roots and other things above the ground that the blade hits and this quickly dulls the blade.
5. Clean deck, engine, and transaxles every use.
6. Wash mower every month.
If this inspection is done in a timely fashion and taken care of then your mower will not die due to parts becoming weaker or breaking causing more damage and will last a long time.
I have an old mower that truthfully, I don't take care of as well as I should. But I furnish it my neighbor to cut his and my yard and he keeps it in his shed. So, I don't have much access to it. It is a 52-inch cut Husqvarna. I had traded for it, and it had about 500 hrs. Now it has about 950 hrs. I have had it about 3 years, and it was used when I got it. It has had only the starter and a deck belt gone bad. It is keep clean and serviced but not as good as it should be.