ACL Surgery

Just echoing the priority on long term recovery. Do all the activity your doc/PT proscribe, and adjust caloric intake to match that. Eat all the calories you need to maintain your weight with the proscribed activities. Don't eat in a deficit when healing. Weight gain increases strain on joints, so avoid surplus eating, too.

Best of luck with your repairs. I tore both my ACLs (at different times) in the late 70's and at that time they were not doing the repairs. Even in the 90's when they started doing repairs it looked like horrific surgery (watched a friend go thru it) so I declined. I avoid snow skiing but other than that and NOT taking muscle relaxants or jumping out of planes I am fine for running, tennis, waterskiing, horsebackriding etc. I will be following your recovery as I am always impressed by the vast medical improvements we make over the years and I bet you have a full recovery. I have met others who's knees were completely unstable without surgery so I get that my particular instance might not be the average bear.

When I was having my ACL replacement, I asked my nephew, who had had the procedure a few years previously, how long it took him until he was recovered. He said he was about 90 percent at one year.
I think that is pretty accurate.
It seems you are getting comment here from people who either did not have surgery (considered a very viable option -- for SOME) and people who had their surgery a while ago. But my sense is that things have changed a lot in the past decade.
My brother tore his ACL playing soccer back in the late 1980s. As he recovered, he did TONS of gym rehabilitation. Exercise bike, etc. After mine, about six years ago, I saw the rehab guy twice. Maybe three times. But the appointments were so brief, they were eminently forgettable. So I don't know. He gave me a handout each time, which gave me directions for a few simple exercises, like jumping from one square to another, and back. Eventually, I think, he also told me that when I finally got ready to go out and run a bit, I should spend a week or so skipping instead, first.
What the heck? I wondered. What happened to the rehab?
So I asked a sports therapist I know, "Why didn't I get extensive rehab protocols? I had my surgery done at the university. They ought to know what they are doing."
They do, he said. But the surgery today is not your grandmother's surgery. They are extremely precise in ways they did not used to be. For instance, they line up the replacement tendon exactly, using lasers, and every aspect of the surgery is arthroscopic (small openings, less collateral tissue damage). For those reasons, you don't need rehab, he said. Now, you just heal from the surgery and you are ready to go!
From what else I know, that is true.
About 6-8 years ago, coaches and rehab specialists were really pushing athletes to get back to sport as soon as possible. Soccer players were being encouraged to return to the field in as little as six months. Adrian Peterson, the NFL running back, was playing in the league again in nine months! Nine months. To professional football!
The experts have since learned, however, that Adrian and those others are freaks. While it is possible, not many people can get back that fast. Now they recommend you follow your own timeline. Some people will be back faster than others. I would guess that one year to be back -- feeling free to do what you used to do without thinking about it (much) -- is average. Maybe a bit longer.
Regarding staying active, that is a tough one. My own experience was a bit different because I had a cartilage defect fixed at the same time which delayed my recovery greatly. But I will guess that if you had only a standard ACL replacement, they'll have you on the exercise bike within six weeks, maybe eight. I used to hobble around the block on my crutches to get out a bit. And, I used to go to the gym and use the machines to do upper body exercises I could do sitting.
As for calories? I was extremely active before my surgery: six-mile runs three times a week, soccer at least twice a week. So I was in the habit of seconds at dinner. I learned in a month that, WHOA! I cannot do that anymore. I gained 10-15 pounds right away.
So I recommend watching your portions and keeping them small. Even if you are trying, you won't be moving very much in the first month or two. First you're in a straight leg cast, which makes going anywhere a hassle. Then you are in a flexible brace, which isn't much better given the swelling. Etc.
But hang in there. You will definitely be in very active rehab within two months, and you will probably be starting to run again in anywhere from four to six months.
Good luck.