Do I need to replace both garage door springs at the same time?

You do not absolutely have to replace both garage door springs at the same time, but it is highly recommended and is standard practice for professional garage door technicians when your door has two torsion springs. The reason is that both springs were installed at the same time, have the same number of open and close cycles, the same age, and have experienced the same wear, rust, and fatigue. When one spring breaks after 7 to 12 years or about 10,000 cycles, the second spring is right at the end of its own lifespan and will almost certainly break within weeks or months, which means you would have to pay another service call fee of 75 to 150 dollars plus labor again. Replacing both at once costs 300 to 600 dollars compared to 200 to 400 dollars for one, so you save money long term. Additionally, a new spring and an old worn spring will have different tension levels, which can leave the door unbalanced, causing it to lift unevenly, go off track, strain the opener, and wear out cables faster. If your door only has one torsion spring by design, then you only replace that one. For extension springs, replacing both sides is also recommended for balance. The only exception is if one spring was replaced recently and the other is still relatively new.