From my little understanding your smerits can only expires when your account got knocked down, that is to say whenever you don't longer have access to your account to operate it this including to make and creates post, reply pm then consider your merits expired.
That's the most simplest and childish reason I have read here till now. Do not mind my words please. But that's an obvious thing that if someone had lost access to the account then he or she can not send merits, even can not make any type of activity on their accounts. But still, it is a reason and can not be ignored.
If op keep asking this question and haven being here for so long then I don't mind saying that this is not the real owner of the account.
Just being curios here, that many members have doubt the fact that, OP might have some smerits airdropped to him according
to this formula. And he is active after a long period of time, so he might not understood the merit system yet. And maybe that's why he is asking around for it. I don't think he is looking for unwanted attention. Maybe some simple answers.
And the thing which I don't understand here is, how can you say for sure or conclude that this is not the real owner, maybe I am not thinking straight or got the point here. But it will be a great help with you will shed some light on it.