I'm kind of an anomaly in that I've owned... 5 reusable menstrual cups (with a 6th en route as I type) over the years. Some people have been curious (not necessarily in a bad way) about why someone might have that many cups. For people who've also been curious, here's why. For people who also own multiple cups, I'd also be curious in knowing what's prompted the purchases.
Small Diva Cup: Purchased in something like 2003 or 2004, it seemed the most appropriate of the 3 available options: Diva Cup, Keeper (original latex model), and Mooncup UK. I have a latex sensitivity, and since there wasn't as much discussion about best sizes then, it seemed to be more practical to pay for shipping to the US from Canada than from the UK.
Small Mooncup UK: Purchased about a year after my Diva, once I'd decided that the discomfort I felt with the Diva was less likely due to a learning curve and maybe more likely due to the Diva being too long for my vagina. In fact, the Mooncup UK was a significant improvement for me, comfort-wise.
Small Lady Cup (Lilac Cup): Purchased around 2008, because I was still feeling my MCUK while it was inserted. I thought the shorter Lady Cup would be more comfortable. And, I will admit, I was swayed by the thought of colored cups... and also lured by EBay. In terms of comfort, I was right: my Lilac Cup is the only cup I own where I can actually forget that it's in place. Unfortunately, its capacity is small enough to require emptying it every 20 minutes or so throughout the first 4-5 days of my period. Not so workable.
Small Yuuki Cup: Purchased in late 2009 because I was hoping to find a cup that held more than my Lilac Cup but that was more comfortable than my MCUK. And, again, the evil that is Ebay lured me with low opening bids. Unfortunately, the small Yuuki only lasts me about 30 minutes before it too runneth over, which is what led to my fifth purchase.
Large Yuuki Cup: Purchased in the last couple of months, used for only one cycle so far (which means my experience with it may yet change). It has a larger capacity, which I appreciate, but also a longer length, which I do not. And the capacity increase isn't significant enough to entice me to deal with the HAI THERE IS SOMETHING HARD RUBBING MY CROTCH sensation that a too long cup produces.
Large Lady Cup (Blue Cup): I do not have this one yes, but it's also purchased from EBay. (Ah, Ebay, stealer of much of what little disposable income I have.) I am hoping that the Lady Cup's smooth base will make it less obtrusive than other cups, so that I'll be able to enjoy its somewhat greater capacity. Because if part of the appeal of cups is needing to use only one menstrual product, then it would be nice to see what that feels like, instead of using 3 or 4 at once.
If your quest for the perfect menstrual product has led you to purchase more than one cup, what factors have influenced those purchases? If you've thought about (or are thinking about) purchasing multiple cups, what factors are you considering?