For each solution ( developer , stop , fix ) I use two trays of the same size and shape. One containes the liquid and the other I put as a floating lid on top when I finish printing. When I start the next printing session I just pick up the top tray and rinse it with some water and all is ready. If you only print working prints you can keep the setup for more than a month ( as long as you don't exhaust it ). It seems to work well with almost all types of developer.
When it's time for exhibition quality prints I mix new chemicals. It's a very convenient way to work and I have used it ever since I started up my own darkroom more than ten years ago.