At 5.1 cm I would talk to a Thoracic surgeon, mine was 5.2 when they found it while having leg fracture surgery, the surgeon saw me a few days after I left the hospital (different hospital), he recommended I had the aneurysm repaired as soon as I could walk some from my leg surgery, 3 months later I had it done, longest 3 months of my life, I wanted that thing gone. I was 54 in good physical health, out of the hospital in 5 days back to work in 3 weeks.

All measurements said 5.2 but the surgeon told me it was larger when he removed it.

I also have a bicuspid aortic valve (contributed to the aneurysm) and we talked about the possibility of replacing it, but the surgeon found it to be highly functional and told me my natural valve is better than any artificial valve he could have installed. I will need to have it replaced at some point maybe 10 years or so, but now it can be done through catheter.

Keep yourself healthy, stay active but not overexert, treat your body well, find the best surgeon you can find and a cardiologist who specializes in aneurysms, hopefully from the same team, it made a huge difference for me. 5 years later I am doing incredibly well, working out regularly, enjoying life with my family.