Firstly you posted a question on a public holiday so those here who browse the web from work will not see your post till Monday.
Secondly you are relying on Tiger Cub owners who have had their hydros fail to respond, and that is a very small number list members.
You have owned the unit from new so should have the owners manual and in the specifications section should be the name & model of the pumps.
If you asked how long could you expect a Monster Mover model 123 pump to run then you have now expanded the number of people who could give you first hand experience as the hydros used in your mower were used in a lot of other mowers but if you don't tell people what hydros you have don't expect others to go to the effort of looking up the spec sheets of your mower to see if they have the same hydros as you.
Hydros used in mowers wear out due to errosion between the piston chest & the valve plate.
Good quality commercial grade units will have a filter which should be replaced fairly regularly and the oil changed more regularly.
Domestic hydros do not have this facility for 2 reasons
1) it adds substantially to the cost
2) lazy owners never bother to properly clean the outside of the units before refilling thus introduce dirt into the unit which negates the purpose of changing the oil in the first place.
People do not understand that the dust which kills hydros is smaller than a human eye can see.
Hydro filters are generally in the 10 to 25 micron range.
Using the Henry Ford principle of planned obsolesance domestic hydros will usually run 500 to 1000 hours.
Commercial units , properly maintined should run 3000 to 10,000 hours depending upon how they are used