On the one hand, airdropped sMerit was created in proportion to each one’s rank and activity, and therefore was respectful with both of these concepts that one gained historically. It is each person’s prerogative how and when they decide to use them. Some accounts will possibly be inactive for a longish period of time, and when they reactivate, they could well do with some sMerits to award.
On the other hand, 15 months of not using them is a fair amount of time, and the idea is not to hoard them. As often happens, the issue is not really the non-usage, but rather the potential mal practice that could become of it. Accounts that have not set the initial sMerit airdrop in motion may not really be bothered with the Merit System, and as such, may just let it be in their accounts, … or decide to trade with it. Of course, trade likely happens with non-airdropped sMerits too, but the aggregate potential amount of airdropped-smerit that exists is large, and perhaps a potential "risk" (i.e. underground sell of sMerits or accounts with them).
Perhaps if we encounter a period of sustained multiple proven merit abuse cases, then some sort of action may be required to reduce the risk, although likely only a small fraction of the cases are detected.
I don't deny that some merit abuse is happening and additional abuse is not detected, but in the end, I doubt that it justifies the implementation of a smerit decay policy...
Of course, unilaterally theymos could decide either way, and I imagine that he would be receptive to evidence that is based on both facts and logic - and such evidence would likely need to show more benefits coming from such policy than the negative aspects of taking things away.... and such evidence would likely have to go beyond the concept that there are "undetected" smerit abuse cases out there or that there might possibly be undetected smerit abuse in the future.