I've been there. I had a couple of sets of major arthroscopies in 1992/93 and 2006, when I was 43 and 56. They have fallen out of favor for OA, but they did each give me another 10 years of less pain and better function, smoothing out the bone on bone. However, there is considerable rehab for those. Importantly, the time they bought me allowed knee replacement technology (prostheses) and techniques (surgical and incredibly better pain management and quicker return to weight bearing and function). So I am glad I waited for those.
But if my knees had held till now, I would just have gone for replacement (knowing what I now know).
I can say 5 weeks out, that even with swelling and stiffness, the replaced knee is the STRONGER one. I have to be careful in rehab not to hurt the other one!
They are big in my area on doing bilaterals close together. 5 days apart, even. I had a roomie in inpatient rehab who had that done. It is less expensive overall and maybe it guarantees your insurance will cover rehab for some days in a skilled nursing facility. Check that out!!! I would never want to do both at once here UNLESS I went to inpatient rehab, as opposed to straight home. You get more intensive physical therapy there (machines, too) and more room to move around and build technique and strength than in a house (than my house, anyway). It really built my confidence. I also have a multilevel house with scary stairs, so no way would I do both at once. But that is me. I plan to do the other next year, after some scheduled travel. It is a concern hoping the other hangs in there, though.
I knew it was "time" when the right knee "went" (maybe tore some calcified cartilage that kept getting pinched) such that I could no longer walk stairs normally and had to walk VERY slowly, with hiking poles if outside the house, for fear of getting an agonizing "pinch." I stopped doing my daily 3 mile walks, I could not walk with my husband on weekends. No way was I going to be able to negotiate large airports, etc. I had a real feeling of loss and defeat, but had to work through that. The knee did the best it could for me for decades but needed help.
Now I am glad I did it. I am not looking forward to the next surgery but am looking forward to having two strong knees. My knee feels like it is MY knee, only better. I will likely have to get new ones at some point, but between now and then I will be in such better knee condition and life ability than before that it is ABSOLUTELY WORTH IT for me.
Best to you in your decision process and recovery.
PS Best thing I did before surgery was get a metal patch test. Hardly anyone gets this. I had some history of unspecified metal rash (cheap jewelry, etc.) so was adamant about this. Only one person here does them, had to fight to get on her schedule. The test itself is a drag, takes a week or more. Turns out I have a VIOLENT delayed reaction to cobalt. Most prostheses are chromium cobalt. Would not have had a good result. Gave my surgeon real food for thought about the merits of these tests.
I have a titanium knee and it is fine.