I tried to find what is an average and a maximum number of courses on a Moodle site. When should I be worried that I got too many courses on the site for the server to handle or for me to manage?
Let me know how many courses you have on your instance and what are the challenges you face.
(I wasn't sure where to place this tread, since it's performance and also administration...)
The number of courses has no direct influence on the required server "capacity". However, course numbers may reflect how many people are using the site (and how much) and how much space you are using for uploaded files (moodledata).