Couple of things:
1) I assume you have a good surgeon, and have expressed how much you enjoy working out and have asked him/her the same question. Yes? If not DO IT. Then take his/her advice, not some moron online like me.
2) A good physical therapist is worth their weight in gold. Again i have to assume the surgeon has lined you up for PT following surgery. If not, WHY NOT?. Tell the PT what you want to do. Physical Therapists who support you desire to return to the gym are equally if not more important than the surgeon. If you get a good one. That degree ain't no walk in park anymore, the good ones go to school nearly as long as your surgeon. GET A GOOD PT. And do what they tell you. And say "thank you"......alot.
3) Your 45, not 35, not 25. Your warranty expired at 40 ( i won't get into that unless you ask, but basically mother nature has no interest at all in having humans live much past 40, in the natural world your just a drain on resources)
You will NOT recover half as fast as 35 or 25 year old. Know that. If you push things you will simply make them worse. A good PT will tell you that. The surgeon doesn't care, cause it just means "more work" for him/her.
4) If you have a good surgeon, do proper PT and take your time, you will not "loss anything" You will bounce back to your previous levels rather quickly once you are truly healthy because you body has already been there once. Your fear of losing "everything" you have build is highly miss guided.
Case in point, Ilya Ilin, 2-time Olympic gold medalist. Set the world record at 205 lbs in the London Olympics (weightlifting). Didn't touch a weight for the next year and a half. As his coach said "basically partied for a year and a half". Came to the states back in December for some cross fit seminars. By his photos he couldn't weigh more than 175 lbs.
After the new year he decided "what the hell, lets go for a record 3rd straight gold in Rio"
Started lifting again and as of last week was 230 lbs and putting 530 lbs over his head in the clean and jerk. Look for him at the world's in November. To DOMINATE.
He could do that because his body had been there before.
5) WALK. Walk, ask your surgeon, after my shoulder surgery my Doc, said
"Do nothing, leave it alone, don't even jog for the first 6 weeks, the jarring will cause slower recovery and damage. Just do your PT'
I read online about how Louie Simmons came back from breaking his back to become one of the worlds best powerlifters and coaches. He said walking was one of the best forms of active recovery, gets the blood flowing which aids all recovery. So i dialed up my doc a week after surgery and said "hey what about walking?" He said fine. For 6-weeks i walked 10 miles a day, then started back into things SLOWLY.
I'm lifting a helluva lot more today, 10 years later than i did before my surgery. Walk.
Good luck and be smart and you will be cool. Just ask the surgeon and PT all kinds of questions and for god sakes don't just take some online morons advice, think about it and ask yourself does it make sense, then ask you doc and PT.