Hello All,
This is venkateswaran, residing in chennai.
I've been a consumer of this forum for a long time till today. For a change, just wanted to be a contributor also. So, is this reply.
As per "Smritimukta phalam" in the Ahnika khandam, It is said, Dharbai that is cut on amavasya day of both maaga and sravana month can be used for the whole year.
Secondary option, any amavasya day. but is valid only for that month.
If it is cut any other day, it is valid for 7 days from the day that it is cut.
Recently i happen to watch an upanyasam that has a full-fledged info on 'dharbai' .Here is the link. very useful. watch it after 32:30 minutes if you are curious about the subject matter alone.
(opps, i dont have post counts to post the link. you can browse youtube, check for 'veda dharma paripalana sabha' channel, and look for " 75thOVUon"Homa Sambhandham- Dharbai , Samithu, Uses of Ghee in Homam etc")
sarvam krishnarpanam.
Venkat.