I'm 50, have a very heavy flow (fibroid problems) and I think I'm looking forward to menopause! I've had one child (vaginal birth). I've bought and used Diva (too strong suction for me), Mooncup UK (fantastic but too small), Lunette (pretty good but not very comfortable) and LadyCup (the best so far for me).
I've found that two circumstances will make the cups leak for sure:
1. flow with small clots, which block up the small holes at the top of the cup, and
2. just before and/or just after a BM.
Where the leaking is because of the clots I've tried making the holes larger but it doesn't seem to help much, although the Ladycup holes are set differently to the others and the cup carries on holding even after the holes get a little clogged up.
Where leaking is before or after a BM I think the shape of the vagina changes and the cup only sits right when the regular shape restores itself. So if I wait a bit after the BM before inserting the menstrual cup it's less likely to leak. This may just be connected to my advanced age (!), I don't know.
A comment about the Lady cup - someone on the list recommended using the C-fold for insertion (something I haven't been able to use for any of the other cups), inserting the back of the C facing the pubic bone, pushing the back of the C up the vagina gently until it goes past the bone and then inserting the rest. I found this advice very helpful, worked like a dream.
Thanks again to all the listees out there!