MyBB Community Forums

Quote:Read Threads in Database (Days)
The number of days that you wish to keep thread read information in the database. For large boards, we do not recommend a high number as the board will become slower. Set to 0 to disable.

Will that delete threads older than 7 days or what?

No, it won't delete it, it's how long it will store information on what threads you have and haven't read.