I noticed my garage door was a bit heavy if lifting it manually.. It would not stay at any open position either.. it would just slam closed. I inspected the lift springs and they all looked good.
I figured they were probably just worn and I should adjust them. I unwound both lift springs and noticed one was tighter than the other.. so it was out of balance. Not that that really matters, just an overall loss in lift. Also I noticed I am missing the center support bearing. Probably why my door makes so much metal on metal noise when it goes up and down. Looking in to buying one of those. For now I lubed it and it sounds good now.
Anyway, I wound the springs to 30 quarter turns. 7.5 full turns.. and it didn't have enough lift assist. Springs are about 10 years old.. so they are towards the end of their life. I wound them to 33 quarter turns.. and now the door will stay open at almost any height. If I get towards the top, it likes to pull all the way open. Not a big deal.
Anyway this was my first time dealing with these springs. If you notice your door is hard to open manually, or your door will not stay open at any position, then your springs need adjusted. If it's hard for you to open your door, it's wearing your garage door opener out.
Here is the video I used. This guys explains it pretty well. Do your research before attempting this and USE CAUTION!!! It's fucking dangerous! Also, I just used 3/8" extensions for my winding bars. Worked fine..
https://www.youtube.com/watch?v=02KaMvcbuDc