What is most important to me I can manage the number of calendars on my site, and the whole site is very fast (calendars do not effect loading speed, I have not seen this anywhere).
It only have one disadvantage, I don't want to display reservation options for every room (advert as they call it). But everything else works perfectly and fast.
Thank you for your kind review. The Advert (room in your case) has an check box option to turn off reservation system in the advert screen in the administration. That option can be set globally on all adverts or it can be set on each advert.