Update on these. THEY DID START TO OVERFLOW AT EXACTLY 2 WEEKS. I contacted Premier Fence (where I bought them) and this is the reply I got:
"I am very sorry to hear of the trouble you have been having with the
mini cups. Yes, we are aware of its cons and what it is, if you were
to unscrew the base on the cup, there is a float inside that does not
hold its seal. After some use, which is what you have noticed, they
begin to retain water inside the float and that just causes it to run
all the time. There is no shut off from the float because its
flooded. So, I would be more than happy to refund your money for the
mini cups. We are waiting to get the improved version from our
manufacturer hopefully soon. I am told. I am not sure when but we
will announce on the website when they are here. Please let me know
what you would like to do. Thank you for your detailed report and I
again apologize for the inconvenience."
So I got my money back. Too bad. I really liked them while they worked. Hopefully the new ones being developed will work better.