Because Access is a rapid application development environment, the maintenance period tends to be much more extended than that for a mainframe or DOS-based application. Users are much more demanding; the more you give them, the more they want. For a consultant, this is great. You just don't want to get into a fixed-bid situation: Because the scope of the application changes, you could very well end up on the losing end of that deal.
There are three categories of maintenance activities: bug fixes, specification changes, and frills. You need to handle bug fixes as quickly as possible. The implications of specification changes need to be clearly explained to the user, including the time and cost involved in making the requested changes. As far as frills go, you should try to involve the users as much as possible in adding frills by teaching them how to enhance forms and reports and by making the application as flexible and user defined as possible. Of course, the final objective of any application is a happy group of productive users.