I think if sMerits will have an expiration date, people will be obliged or will become more active in giving merits to others instead of losing it, this will actually helps many members like me.
No, it won't help one bit. Why? Because it's of no consequence to the person whose merit is going to decay. Do you think anyone really cares if they run out of smerit? I'm a staunch supporter of the merit system and I've tried to give my smerits out judiciously, but if I lose them it's no skin off my back. And do you think the average bounty shitposter is going to care? Probably not unless it means he can't sell them, and that's not going to help the people who deserve to have their posts merited.
I think having smerits decay is a silly idea. The only thing it'll mean for sure is that there's less to go around, and there already isn't enough.