When you have a Touchnote membership, you get credits every month. The company understands that you may not use all your credits every month, so some plans allow you to carry the credits over to the next month.
If you have a bronze membership, you only have a month to use them. When the month is up, your credits expire.
For silver membership, your credits will roll over to the next month for up to 3 months before expiring.
Gold and platinum membership credits roll over for up to 6 months.