Why? You and the client jointly agreed on a certain quality standard and you met that quality standard. This should have been indicated by a client sign off.

Why? You and the client jointly agreed on a certain quality standard and you met that quality standard. This should have been indicated by a client sign off. The only way I'd say you owe them in some sense at this point is if you clearly didn't meet the agreed upon spec... but the tests (both code and user) should have hit most of that. After that... well, they need to evaluate the cost/benefits of changing the software. Also, do not fix bugs for free -- certainly, people have done a (very tiny) bit of work for good clients, but you don't want to train clients to expect free stuff. You'll find that clients also try to slide features in as bugs -- the best way to keep a cap on this is to do a good job, meet your agreements, and then force them to decide on whether any further work is worth your hourly rate.