If you start right now you can also use the .net 8 preview version. It will be released in November, so if your production use starts after nov 2023, it should be fine.
We use .net in production and we upgrade to every version. I think we went from .net core 2 to 2.1 to 2.2 to 3.0 to 3.1 to 5, to 6 and now we are on .net 7. Every time it was a bit of work but this is an ongoing project so some maintenance is to be expected.
So yeah, if you want fewer updates go with LTS and only upgrade to the next LTS version. As they come out every 2 years, you have a whole year to upgrade from one to the next one.
Note that also customers do not always like stability. "Works with Windows XP" might have been cool back then but the real requirement is "works with todays windows and the version prior" or so. Nearly all requirements shift and an application that is not maintained and updated will loose its appeal in a few years time.
Constant app maintenance is a recipe for success and upping the .net version from 6 to 7 to 8 can be part of that.
If you deliver your application in a container, your customer does not even need to care about the .net version.
So a summary: If you want a long support period, choose .net LTS with 3 years support. That is the long support period. The short one is 1.5 years.
Edit:
On top of that: You should strive to update your app much more often than every 2-3 years. For one because maybe you created a security issue, but maybe for other reasons or limitation. So ideally you arrange a regular update window and some of the updates include updated dependencies (like a .net version jump)
For example, I had an application where I displayed a sum of filesizes in an int32. Broke after 7 years and 2GB of files and suddenly they wanted a fix. Would have been better with more frequent updates and internal monitoring of limits.