My cup rarely leaks... even if it is overflowing full it will still not leak. The exception to that is is I do something... bike riding, laughing hard, etc., that may momentarily cause release in suction (and would not normally leak) which causes tiny amounts of overflow to come out.
Usually I can tell when my cup is full because I can "feel" it. But if I'm not paying attention, than I know it's full when I wipe and actually see blood (even though nothing is on my panties).
I normally empty my cup before it overflows, because normally when I empty it there is no leaking and mess. If I let it overflow, then removal is not so clean & quick. Most often if it gets too full, it's at night on a heavy day. It's nice sleeping through the night instead of waking up in the middle because I'm wet, like what sometimes used to happen, though.
Anyhow, I was wondering, what happens when you cup is overfull? Is it just the diva super-suction cups that still don't leak, or do they all do this? I'm not actually complianing, it's nice.