I had noticed that I was having to log in several times per day. I'm curious to know if anyone else is having this problem? I was able to fix it by clearing my browser cache for thereminworld.com.
If you're using Chrome on a Mac, then you can do this by hitting Option+CMD+I to load the developer toolbar. On Windows hit F12. Then right-click on the page reload button and choose "Empty Cache and Hard Reload".
Let me know if you have the problem and if that helps.