The old releases don't become pumpkins immediately upon release of a new one. Things were different around 10, but nowadays, the support expectations are pretty clear[1]. FreeBSD 12 support ends at the end of this year, so not a good choice for new users; FreeBSD 13 support is expected to end in January 2026, so if you install today, you don't need a major update for about two years. That's plenty of time to try it and see if you like it. If there's a critical feature in the upcoming release that you'd like, RCs are available in advance of release, but IMHO, I wouldn't suggest that as a matter of course for a new user; sometimes RCs have rough edges and that's not a great intro. But you know, up to you.

In the past, waiting for an X.1 release was advised by some, but I don't think that's necessary anymore.

[1] see the supported releases table https://www.freebsd.org/security/