I have had mine for over 2 years now.

The filter catches most of the floaties you might otherwise find in the
water. I refill mine with filtered water from the fridge.

Because the water is circulating and getting oxygenated it really
doesn't go stale or bad... you can likely get along fine with giving it
a scrub every week or so.

We have a similar fountain, Petmate I think.

I add fresh water daily, an I clean it with hot soapy water once a week.

Brad

I have a Drinkwell at work for the two office cats.  I take it apart & clean
it once a week.  At home, I have a Freshflow (?) for my two cats.  I have to
clean that 2-3 times a week.  Anything that falls into the water (fur, food,
bits of paper or whatever) just sits on the bottom of the bowl.  I really
wish I had bought another Drinkwell.

Liz

Paul Enterline <enterline@ce.net>, with thought and calculation,
said in rec.pets.cats.health+behav:

I have a Petmate and I clean it every two weeks.  I have a bulb syringe
that I snipped part of the end off to make the hole bigger so I can
just suck out the crumbs and stuff that fall in there.  I can tell when
it needs cleaning because the top on the reservoir starts to get a
little slimy.  I'm still trying to figure out what genius engineered
this thing to filter AFTER the pump instead of before the pump.