I have been writing Microsoft Access software now for nearly 25 years. In that time I have occasionally had software projects that have not had any development or support for 5 years or more. If the project was small, starting again is no trouble. If the project was big, getting back on top of the project is either costly to me or the customer.
After 5 years has gone by, the customer will be familiar with what some of the software does but may not be aware of the workings/specifications for the software, especially if they are new to the company. If so then everyone who is going to be involved in the new development will be "somewhat in the dark".
Things can get start to get a lot darker when the programmer of the software leaves town. Given that there has been no action (read money) for five years, there is every likelihood that they will have left town. This particularly applies to contract programmers who are working on the next project the minute the current contract is completed. My company doesn’t do contract jobs for that very reason.
What is the solution to this stagnation dilemma ?
My personal belief is that software is like a pot plant, it needs watering from time to time or its going to die eventually. If you only have a set budget for software every year, there is no need to rush, just do 20 hours a month rather than 100 hours all in one month and then stop development. If your programmer / consultant cannot provide that style of service, maybe you should look around a bit more. Over the thirty years that I have been programming, I have noticed that the best projects are the small and gradual projects where the sponsor of the project thinks carefully about the next enhancement, briefs the programmer and does the testing whilst not being rushed. You will not be surprised that many of these projects just keep ticking on for ever and the customer is happy because their working life is always improving.
"So go water that plant" - Garry Robinson, editor of the popular vb123.com.au