Yes, parts in-service for water regulation in your commode wear-out. Ten years of service? I'd say, that's getting your $'s worth!
I just used to replace the parts with Fluidmaster when they needed replacement, and I kept a complete kit in-stock at home. That includes the shut-off valve, the supply line, the flapper valve, the tank to seat foam valve, brass tank to seat machine screws and nuts, complete with rubber washers and plastic washers, the red-tower Fluidmaster water-control, about the only thing I didn't keep on-hand was a handle. I figure, all the other parts can cause a leakage problem, but I can flush a toilet by-hand, overnight, if the handle breaks or the chain snaps. No big inconvenience or loss of function until I can get to the hardware store the next day.
I used to solder the appliance shut-off valves in-place, but now it's compression fitting time. You can switch one out on probably less-than 5 minutes. Ever since they went to the non-replacement rubber washer gasket, chrome-plated brass valves, when the metal decomposes because of your water characteristics, and you have to replace the valve, it's a long process to solder-in a new valve, and I use a plumber's acetylene 'trench-tank,' not a propane or MAPP gas torch. When I say, "long-process to solder-in a new replacement shut-off valve," I'm comparing it to undoing a compression fitting, and installing a new one on the wall-out stub. A pair of slip-joint pliers for working both the supply hose and the shut-off compression fitting, versus: to solder:crocus cloth, solder, flux, a gas tank/burner, a brush, maybe a rag, an insulating blanket for the heat, it's just a lot easier to use a compression fitting shut-off valve.
Now, I have used the expediting tactic of just unscrewing the compression nut securing the entire valve stem assembly, with its captive, no-machine screw retaining 'nub' that holds the washer in-place, and just slipped on a new valve stem, re-using the soldered-in-place shut-off valve body. That works, and is an 'expedited' method of restoring shut-off valve function. But, upon removing the old one, and seeing how the water has deteriorated the old valve stem body and washer retainer, what sort of deterioration has the valve body undergone? Kinda like playing Russian roulette. So, it's better to replace the entire body, but I've done it the stem-replacement way, I even bought extra valves so I'd be sure to have the exact same dimensions in the replacement valve stem, if I chose to do it that-way. But, now we have new plumbing in four new bathrooms, and they're all compression fittings on the shut-off valves, to make a job simple 'the next-time.' I'm hoping that when that time comes, my decade will have an "8" in the "tens" place. That's less-than fifteen years... . And, I hope that my TOTO Neo-Rest will be helping my personal needs past that-time.
I like uniformity in fixtures, but when we re-did our home, my wife was very specific about what she wanted. We went to Ferguson Plumbing, and she chose two different Kohlers, a Mirabelle (which I think is a Ferguson in-house brand), and a TOTO Neo-Rest which having-posted about this fixture before, raised indignation among some members of the forum. It's powered by electricity, no tank, so it needs a larger water supply line to provide the volume. And it has an air filter, a fan, and it combines the functions of a bidet, with temperature-controlled seating, air, and wash water.
https://www.totousa.com/neorest-750h-dual-flush-toilet-10-and-08-gpf-with-actilight
Oh, and it flushes itself once you depart the throne. Sheer decadence! Be sure to familiarize-yourself with the price as this seemed to be the objection of those who 'doth protest, mightily.' It has a remote control for all these functions.
https://www.totousa.com/filemanager_uploads/photo_gallery/neorest_550h.png
One of the reasons we chose to get such a unit, was that we just finished caring for my in-laws at the end of their lives, and having this type of toilet will allow us to 'age in-place' longer, and to be hygienic about it. Well-worth the investment, for the results.
