I'm very sorry for the delayed response. We had a high volume of support requests since the release of v1.9.
For more documentation on feeds, please go here: http://help.time.ly/customer/portal/articles/504373-how-do-i-import-a-different-calendar-
There is no set limit to how many feeds you can import.
Your feeds will not be deleted unless you manually delete them. Otherwise, all old events will stay in the calendar. We may improve this down the road but, this is the way it works for now :)
Thanks