its a good question, for me I had one that got 90 days out on one invoice, 76 on one, and so on down from 14 day increments all the way down to 0. It was a new account and I had to place the call, they are also the owners of another franchise in town thats notorious for paying their greaser extremely late almost to the point of when they feel like it. After that call were caught up, back on schedule and there is a check in the mailbox every time I do them or within a few days of cleanings.