I have used Hubspot for many years. Earlier in my use of it, I requested to have the number increased of calendars that could be connected for the purpose of showing availability in the meeting scheduling pages. It was increased to 50 and this served my business needs for many years as I grew my business.
However, I now need to have more than 50. These are all Google calendars which we create for each of our clients when we begin a campaign with them. Because I am a part of all the meetings and events put on the client campaign calendar, my meeting scheduler needs to reflect any and all events on all the campaign calendars.
I have encountered no performance issues with number of calenders we have attached.