Two or maybe three things
My DH had the op 5 1/2 years ago and while all the heart issues are fine, (apart from dizzy spells, AF, giving up driving and breathlessness,) it was a long slow recovery and he has other problems which are in turn terminal and may be may be much more distressing. His quality of life deteriorated sharply, but to be fair there are other issues.
My MIL died in her mid 80's of a ruptured aortic aneurysm suddenly one morning, it looked as if she had gone to sleep quite painlessly while quietly reading the Sunday paper in her armchair. She was staying with her daughter ( a GP )at the time.
My sis in law had a patient not that long afterwards, late 70's, poor health but had been advised he needed a graft/repair of an aortic aneurysm. He asked her opinion. She told me afterwards that of course she had to give her professional opinion, outlining the pros and cons, the risks, the dangers of the operation, the effects on his life afterwards even assuming it was successful and of course couldn't give her PERSONAL opinion based on her mother's sad, but quick and painless demise. Personally she would have told him to go home, enjoy life and enjoy his family for as long as he was granted knowing that when the end came he would know nothing.
But who of us can make that decision. Do make sure your DH gets as much information and advice as is available before he makes his decision.
Your DH is being a brave man and you are being a brave wife.