Ok, so I'm looking at taking the plunge, but I want to know more first ...
What cup do you use?
Mooncup
Why?
Was the first brand I found and I liked it. Have had it for probably close to 8 years now and not needed to buy a new one.
Do you have multiple sizes, or just a medium / large one that you change more often during heavier flow?
I have the size for women who haven't had a baby. The capacity isn't that different, it's just the diameter as your bits are different post birth. They hold a lot. On a heavy day, I still only change every 3 hours or longer. On day 3-4 only change in morning, after work and before bed.
What on earth do you do if you need to change it in a public bathroom or at work?
Honestly, you get the hang of it. Once you practice a bit at home, it gets easier. I make sure there is plenty of loo paper available. If there is no sink, I simply wipe out with paper and reinsert. I have a disabled toilet at my work so I can rinse if I need to.
How long do they last (as in years)?
Answered above, many years.
Do they come with a storage case, so you can pop it in your bag in case of surprise periods?
They come in a little cloth pouch with a draw string.
Can you wear them overnight (as long as you're sleeping less than the 10 hours allowed)?
Yes, I do all the time, I also didn't know of this 10 hour rule. Unlike with a tampon, there is no air in there so there's not a toxic shock risk like with tampons. The only smell with a moon cup is the smell of blood. Occasionally if heavy I leak when I get up in the morning, but not often. I wear mine to swim as well without issue. Beauty of it is you don't have to change as soon as you get out of the pool like with a tampon.
I wear mine if I am going somewhere and think af might come. there is no danger whatsoever in wearing without your period. I had to use a tampon recently and it was awful in comparison.
Do tell ...
I love mine. It is easy, convenient, none of that icky tampon dryness. I still believe it makes my period go faster. Yes it takes a bit of practice to get in and sealed, but it really isn't that hard to do and yes you may have a 'I can't get it out' freak out, but you will!
Interestingly, when I was in Cambodia earlier this year, I was chatting to a lady about what women do in the villages, and these are becoming one of the popular options in 3rd world countries - with NGO's supplying them.