Hi, Craig...

<< If your client wants you to slip-stream a new feature, have them pay for its development. This would be an additional cost over any maintenance and/or upgrade fees. If they can't or don't want to pay, then they will have to wait until you get the next release out the door. >>

Interesting idea...

Our situation is somewhat unusual in that each corporate client purchases a corporate license to our product. Once they purchase the license, they get upgrades for free. But the billing idea if they really want something in between updates is a very interesting idea. Because 'slip-streaming' is really against our internal interests, we could set the billing such to discourage requests between quarterly updates.

Thanks,
Kevin