Toto has two valves made for them on that toilet that I'm aware of (may not be exhaustive). One of them is the Korky, not sure who makes the other one. Are you aware that on the Korky, generally the only wear part is replaceable in about a minute for about $3? to minimize the water wastage, Toto has the valves fine-tuned to balance the tank/bowl fill rates so both fill at the proper time. Otherwise, you either end up with too little in the bowl (compromising performance), or having the excess just go down the drain. If you are on a well, it may just be some debris that gets caught in the seal, and if you clean the filter and the seal, it may go for another year. If it is because the municipal water supply uses a high concentration of chemicals, then you're stuck...rubber parts age quicker when they are present.