Welcome aboard.
5.5cm is indeed pretty much the time that risk of a rupture becomes high, so I'll expect that they'll do something surgical for that soon. I had my homograft (still functioning) for about 20 years when I was identified with an aneurysm too, and they replaced the valve.
I don't know if you know this already, but if you had bicuspid aortic valve then chances of an aneurysm occuring later in life are significantly greater than for "the general population".
The good news is that they do "bental procedures" now and that will give a high likelihood of quite a many more years before any further issues with that part of your plumbing. I had mine done about 10 years back now (which was my 3rd OHS).
Pretty much all valves that are put in (my homograft excluded) are artifical. I now have a mechanical, which necessitates that I take warfarin. This has not been a significant issue for me and I think its fair to say that it can be managed well if you are so inclined.
I'm guessing that the pig valve you mention is the one in your pulmonary position and that you have your pulmonary valve in your aortic position. I would expect that they may consider changing that valve when they do the aortic aneurysm repair surgery. One of the important things now is to minimise the duration of the surgery (longer runs risks of harm) and to also deal with scar tissue which will be present from the previous surgery.
Did you have any surgery prior to 1996?
Anyway, plenty of us here (like
@Superman ) have experience in surgery that spans a lifetime if you have any questions or want to chew the fat. I had my first OHS in something like 1974, second in 1992 and third in late 2010. I've managed to live a pretty full and interesting life and so I anticipate you'll continue to do as well too.
Best Wishes