I fall in with the rapid succession camp.
That red bag is calling to me before I even get off the commode. Often I have the next pitcher of solution at the ready so I can fill the bag quickly and get to the next fill I know I will be craving.
Sure there are times when I get preoccupied, have other things that take me away from a session, or simply want to relax for a while between fills. But more often than not it is one enema immediately following another.
Heck, when I'm finishing a session with a round in the shower I don't always wait until I've completely expelled the last bag before starting to rip in the next one.
Whatever feels right, ya know.