There was the initial distribution of merits and smerits and the rippling effects of the initial distribution would be expected to carry on for a year or more for members to use their merits and then the halvening too, like you mentioned. 

Yet, there are also 57 members that Theymos has designated as sources of about 12,000 smerits per 30 days, and Theymos seems to think that smerits flowing through sources will cause a sufficient enough supply of continued smerits rippling through the forum, yet it seems that it could take several months to determine how the merit system is playing out in terms of ranking up and flow of smerits, etc. 

I doubt it will dry up, but there could be questions about whether it will be fairly distributed and what kinds of posts will attract the giving of merit.