So far, about once every year or two (or more in the case of the terrarium set-up)
I clean the entire thing. Water evaporation is very low compared to when I was doing the tray system, and so no, I don't change the water much, if at all.
The shelving water'ers will be a discovery, as the trays are clear, which may allow some algae or moss to grow, but I will find out. So far as shown, the holes/drippers do grow some moss after about 6-12 months, which seems to be either sphagnum babies or some other moss. It doesn't affect the watering until it gets really heavy, which this time was about a year & a half.
The terrarium bottom is opaque, so no light equals no growth. There is also a sheet of landscape fabric lining the plastic grid/shelf that the plants sit on. It does get some sphagnum growing on it after a long time, but nothing underneath. I don't know yet how the ones I have on my shelves will do as I mentioned.
The only regular thing I do is to add a little water to it, so far about once every 10-14 days. I sometimes add ferts/tricho to the reservoir, but that can get tricky if I am not careful what plants I have in the system at the time.
I will try to post some more pics soon, perhaps to follow some of the growth & what takes place.
Thanks again for looking & the interest
"Knock on wood" the shelving self-watering units are doing well, and will also post some pics on those later too.
As I mentioned before, it really makes growing most plants a lot easier with a lot less regular work, and it also thus makes it possible to grow more plants. For those who like to tend to their plants daily, that can be a bad thing, but for me now, it gives me more time for starting seed, repotting, trimming, and just looking, along with other things.
I would again recommend people try a small pail/container with a pot on top, and a small table fountain pump & timer for starters. (A simple tube from the pump wired in place to the base of the plant or into the growing medium is all it takes.) Even just to grow some sphagnum. it works great.