I have over 80 days of read time on another forum, which is over 2 months. But I have seen users with 3 and even 5 months of read time, yet they don’t show as 90 or 150 days.
You’d have to look at the code; it’s open source. There’s probably a shared function that determines the correct length of time to show.
This looks like the responsible snippet
since 81 days is around 116640 minutes, which is less than 129599. Thanks!