But unfortunately, I don't have any sMerit to send. The last merit I had received (as you mentioned), was decayed or expired or gone before I log back in in Bitcointalk. I didn't get to spent it. This happened to me before as well. I have received 11 merits so far and I didn't get to send any merits. That is why I'm interested to know how long I can have spendable merits?
Don't worry about expiring sMerit. I can assure you that no sMerit of any user was decayed yet. All of sMerit are in safe, and I guess that there is no any reason to burn sMerit. Simply, you sent your sMerit a long time ago, and these merit transactions are not shown in the list.