Monthly means servers are stable for longer and gives me more time to work on bigger changes, but is more likely to need multiple patches which is perhaps more annoying than weekly.
Weekly or every second week is annoying for many players because servers have to restart for them, but in general they're less likely to need a patch/hotfix. (for example because there are less changes overall to have unexpected interactions)
For example, more than a month before yesterday's update I made a seemingly minor fix to handle newline ('\n') in unquoted strings. By yesterday I had forgotten it was even part of this update, lo and behold it caused issues in quite a few mods!
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