Extension Spring Replacement: what to note first

Open the door by hand and it drifts back down on its own, a little at first and then all at once. Nothing is broken that you can see, but the springs along the tracks look tired, rusty and slightly sagging.

Worth answering before the call

Is the door closed, fully open, or stuck partway? Does the opener still move the door, and does it sound strained? Is it a single or a double door, and what is it made of?

Would a stronger spring make the door easier to lift?

Not in a useful way. The aim is a spring that matches the door's weight, so the door holds still wherever you leave it. A spring rated above that weight pulls the door up on its own, makes it hard to close, and leans on the opener to hold it down. A spring rated below lets it sink. Matched springs, set to the same hook position, give the light, even feel you want.

I added insulation and windows to the door. Does that affect the springs?

Yes, and it is one of the more common reasons a pair of springs is suddenly found wanting. Insulation panels, glazed sections, a wood overlay or a new steel skin all add weight the original springs were never chosen for, so the door grows heavy and the opener strains. When the springs are replaced, the door is weighed as it is now, and the new pair is rated for the door you actually have.