What size tanks do you have that your able to always top off with a bucket? I can tell you this, Id have to hire someone to top off my 180 in this manner. Before I had an ATO, Id top off before I left for work and by the time I got home my return pump was blowing bubbles, my salinity was flucuating way to much, I had to go ATO.
I think the key here is not if its automated or not, they key is diligents. Keep your equipment clean and monitored and these types of issues wont happen. Id much rather take 1/2 hour everyday to check for leaks in the plumbing, check for salt creep, clean my glass, etc, rather than letting it go and ending up spending hours on my days off. Ive learned through do diligents the tank is much easier to maintain, I seem to spend less time on it and am able to enjoy it alot more. I will always have automated systems in my tank, my work load does not allow the time for me to manually do everything, and with this comes the responsibility to make sure all these system are working correctly.
I personally clean all pumps, ATO & skimmer once a week, even if they dont look dirty or appear to have build up, if I said it once here Ive said it a thousand times, Id rather be safe than sorry.