It turns out that this is not that easy. I have two options,
- Disable post edit time limit, which is currently set to 60 days.
- Change individual posts to Wiki posts
The first option has the potential drawback, that posts might get vandalized in case a community member looses their mind for a minute. We had occurrences of that in the old forums and it's quite ugly and is time consuming to clean up.
The second option has the potential drawback, that anyone starting from trust level 1 (Basic) can edit the post. However, you'd be notified by the system if someone would do this and the edit history always shows what has changed. If something unintended has been changed, you could always flag and notify staff.
I prefer the second option right now. What do you think?