No point in a contract! just have a on going agreement (last many years), then it doesn't have to be renewed and give them the opportunity to look else where
When we put a quote in, we get them to sign at the bottom (see below) this covers you if you had to take them to court for non payment
Andy
If this quotation meets with your approval and you wish us to proceed with the work, please sign and date one copy and return to the address below.
Please commence work on (date)
Frequency
Name
Signature
Job title
.