Merit system has been in the circulation for almost 5 months and as of now the issue of earning merits for new members and even those who have been here for a long period is still a hot topic.
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.
If they have an extirpation date then I would probably just give much more merits for certain posts ie double or triple them instead of just handing out 1-5 per post. I certainly wouldn't just desperately give them out to any old random lower-ranked member just because they're going to be wasted otherwise. This suggestion really won't help you out at all unless you're making quality posts and are already receiving merits. I would work on the quality of posts rather than trying to change the merit system because the former will be more fruitful here.