The source sMerit will come back in 30 days after its spending date. If you sent 5 source sMerit on 18 March, you should receive 5 source sMerit again on 18 April. So if you spent it daily during the previous month then you'll receive it every day in the next month.
Oh. I thought you received everything at once after each (fixed) period of 30 days (just like how the activity periods work).
Thanks for the info.