The processing contract length determines how trapped you are. Month-to-month means you can leave anytime with no penalty. Multi-year means an ETF (early termination fee) if you leave early. The industry trend is toward month-to-month, but POS-bundled processors (Toast, Clover ISOs, Lightspeed) still routinely lock merchants into 2- or 3-year deals because the POS hardware investment makes switching painful anyway.
What to read in your contract: term length, auto-renewal language ('this agreement automatically renews for successive 12-month terms unless 90 days written notice is provided'), and ETF amount. Auto-renewal clauses are how merchants get re-locked without realizing it.