I'm a gay man in my 40s who has always been exclusively a top but I have been fantasising about switching. Is it weird that this is coming up now after so long?
Impact PlaySexual interests and role preferences shifting in midlife is very common, and there is nothing unusual about a desire emerging now that was not present before. Many gay men describe discovering an interest in bottoming or submission significantly later than their primary role was established.
Role preferences in gay male sexuality, and in kink more broadly, are far less fixed than they are sometimes presented. The top/bottom binary carries a lot of identity weight in gay culture particularly, which can make shifting feel more significant than it actually needs to be.
Midlife is a period when many people report that their erotic interests become both clearer and broader. The defensiveness or performance-pressure that shapes younger sexual choices often decreases, and what actually appeals rather than what felt appropriate can become more visible. A shift in what you fantasise about at 40 is not a disruption of who you have been; it is new information about who you are now.
The gap between fantasy and practice is worth thinking about separately. Some people are satisfied to hold these fantasies privately; others want to explore them. If you are considering exploring, a conversation with an existing trusted partner or, if that is not the context you are in, honest disclosure in any new connection is the obvious first step. There is nothing about this that requires explaining your whole history.
Within the kink community specifically, versatile and switch identities are thoroughly normalised, and the range of experienced tops who are newly curious about submission is large enough that you will encounter others navigating the same territory. The idea that roles must be consistent across a lifetime is a social convention, not a fact about people.