You should allow in as many users as you can handle the support and feature requests for. One user can take up to 90% of your time, other times ten users come

You should allow in as many users as you can handle the support and feature requests for. One user can take up to 90% of your time, other times ten users come in and happily use the software with no complaints. Take their feedback with gmail. Don't get too fancy. Proactively ask for advice and comments. Sometimes people don't complain until they leave.