Do you want this is a chart or in the script?
I am assuming that you have ID also in the eventdate table to link data.
in the script you can do a group by resident table:
MIN(Eventdate) as 'First Event',
MAX(Eventdate) as 'Last Event',
if(MIN(Eventdate)<=ADDMONTHS(MAX(Eventdate),-10),'Over 10 Months Active','Under 10 Months Active')
Resident Eventdate Group by ID;