Yep, you do have to empty and clean it frequently.
I keep some in a baby food jar. I have a big hole cut in the lid. There is a hinged cover soldered to the top, with a tab on the little cover so I can just flick it with the brush to open it. When I am done painting I close this little cover. Cuts down the evaporation when not painting, yet easy to dip brush in when I AM painting.