Controllers here in southern CA
do not do Radar. However, We do switch positions from Local to ground, to Clearance, to Cab assist, back to ground ect...We do not spend too much time on one position. Towers that have an up-stairs and down stairs (tower and radar in one) IM
not sure, I've never worked in that kind of place. I would imagine they would since the longest you can spend on one position is 2 hours.
So in response to your post, yes we are all checked out on all positions in the tower, and we do switch off throughout the day.