I think it's daily.
Isn't he talking about the sMerit given to merit sources?
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.
So, how about member which not become merit source? Are they only receive sMerit by getting merit from other?