unfortunatelly the calendar creates script object for every instance.. So seems we could not influence the perfomance more than already done.. If you use calendar in the table - you could try to organize something like inplace yourself. I mean to load calendar only when its need to edit data.
Yes I was thinking about some workaround like inplace rich calendar
or some lazy calendar initialization (initializing only when the popup is opening).
But I hoped someone could already have done such thing.
Do you have some clue on what is the best way and how to start ?