Thanks for the responses.
I particularly like Kurt’s idea of a text file with notes about the installation.
I suppose it comes down to how much the client is prepared to pay and the level of service they want. I think it would be good to offer an update/review package after 6 months say, to check all is OK.
EDIT
Interesting that after posting this I checked for build updates and there is quite a list of bug fixes, I would have thought that it was quite likely that existing installations would have come across some of these bugs and had a problem. Would this not reflect badly on the developer?