No one can tell you the correct answer except the admin who introduced the merit system.

Merits system can be here for quite long as:

1) After the merit system was implemented a lot of new members also stared making quality posts. The content length increased from one liners to more. We was  lot of members taking out time for creating useful threads like stats related to merit system. The meta section once again became alive with huge participation from a lot of members.

2) I think it is designed in a way that it will keep getting better with time.