How Long Can Mortgage Co Charge Me 1/6 Extra on My Monthly Escrow Amount to Cover Past & Future Tax Increases?

mortgage

My property taxes went up just after my mortgage company made the annual tax payment to the county. They’ve since raised my monthly escrow payment by 1) the amount of the tax increase and 2) an additional 1/6 of the new escrow payment to cover the past 11 months of increased taxes as well as “future increases”. I know this is standard practice and legal, and I could see allowing it for a few months beyond paying for the past costs incurred, but how long can they take up again to charge me this additional amount? Seems like after several years, they would have banked potentially quite a bit at my expense.