This is basis you having time / bandwidth to spend on the work again.
Set expectations that You will work on the line items subject to option 1 - Bill them for the time spent.
If the support clause you had (if any) has expired, any re-engagement is treated as a new work order and will be subject to clauses and terms that are in effect at the time of signing the work agreement.
This is inclusive of and is not limited to
1. Changes in pricing
2. Changes in support and after sales support clauses
3. Changes to engagement rules and principles - who will work on it, how long, etc.