As others have pointed out, there could be a specific reason specific to your case leading them to do CT scans every 2 years. I have follow up echos. My last one was a little over a year ago. My cardiologist indicated that because I am mechanical, we can go to echos every 5 years, if I want, but he is happy to do them more frequently if I prefer. My call. I'll probably get them about every 2 to 3 years. The nice thing about echos is that there is no radiation exposure. Tissue is a totally different kettle of fish. I would probably want annual echos if I had a tissue valve. Once SVD starts, things can progress quickly.
On the bright side, many have to wrestle with their providers to get CT scans- they're expensive. You team seems eager to do them frequently. But, if they don't have some reason specific to your condition, as to why they are doing CTs every 2 years, I would push for echos instead. It makes me wonder if they have their eyes on another potential aneurysm which the echo can't see. There are some parts of the aorta which are better viewed by CT, rather than echo.