Most of the commercial calls we get from this part of the area start the same way: the door is slow to close, or it reverses partway and won't seat, or it's making a grinding sound on the way up. On a building from the 1960s era common to this town, that's very often a torsion spring losing tension or a bent track from years of a forklift or delivery cart clipping the rail - not the opener, even though the opener usually gets blamed first.
Cold-weather stiffening plays a role too. In a cold, moderate climate band, grease that's fine in September gets thick enough by January to slow a door down and make a healthy spring look like a failing one. If your door has gotten noticeably slower only since the temperature dropped, that's a maintenance call, not a parts call - and we'll say so rather than sell you a spring you don't need yet.