I've searched here in Bitcointalk before posting my question. I've found a similar thread but there were no certain time frame for how long I am able to send my sMerits. Please someone inform me. Thanks.
As long as you have minimum 1 sMerit, you can send it to anyone. This page will help you to see your spendable merits:
https://bitcointalk.org/index.php?action=merit