XF 1.4 Alerts

Is there any documentation on alert expected and not expected behaviour when interacting with a thread by either posting / creating it?

Not interested in conversation alerts just threads.

I seem to be having an issue where alerts will be given for a thread you created / posted in but then after a few replies the alerts stop coming unless I interact with the thread.

Just wanted to see what is normal / expected behaviour and if this is documented anywhere?