I think there are likely a variety of contractual options other than "24/7 phone support" which businesses would be happy to pay for, on an ongoing basis. For example, you could charge $500 plus $100 per year for "maintenance", and not be any more specific than "the software will be maintained in an ongoing fashion", and now you won't be starting from $0 next January 1st. As someone who has started from $0 every Janu…
One is our own product that is very costly to maintain (reverse engineering third party applications) and some customers agree that they need to have this additional service.
Another one is for complex application virtualization. For example, we give the technology for virtualizing IE6 on Windows 7 and 8 but some Microsoft updates break the solution and the company needs to have an "insurance" against that.
Simple support gives a lot of headache.