Thank you for asking your question on Just Answer. The life of a toilet wax seal would depend if the toilet was firmly attached to the floor. It the toilet is loose the wax seal could be damaged very easily, very quickly and it's useful life would be over. With the toilet firmly attached to the floor the wax seal would have an indefinite life.
This would indicate as I stated above. The toilet was not sitting securely on the floor, allowing it to move and this movement damaged (flattened) the right side of the wax ring. The bolts that attach to the toilet flange have to be correctly tightened. If they are tightened to tight they will crack the base of the toilet. After a toilet is installed, often these bolts can become loose, as the wax ring becomes compressed. If not tightened, the wax ring will become damaged as indicated in the plumber's billing.