Bought a house from 1972 in Cleveland last year. Noticed the garage door header had a 2 inch sag over the middle. I jacked it up an eighth inch at a time over 3 weeks using a bottle jack and a 4x4. Did that actually fix it or did I just make new problems for later?
...which reminds me of when I tried to level out a settling porch on my folks' old place down in Parma. I used a car jack under the main beam and cranked it up maybe a quarter inch every couple days. Took me about two weeks total. The porch looked great for about six months, then the whole thing shifted sideways and cracked the brick steps. Turns out I was just pushing the problem around instead of fixing the footing underneath. I'd keep an eye on that header for any new gaps or cracks near the jambs. Sometimes slow jacking just makes the wood and nails settle into a new weird position.