I dont even know someone who uploads everyday I'd say more than three in one week is too much. It makes me so happy when I see a new work of an artist I like when there has been a while since he/she doesnt upload. When I see too much stuff from the same person, if it's not someone I really like I barely look at it.
I voted everyday, but eh.. It is kinda really annoying sometimes. Or I'm too weirdo, lol. Around one month ago I did a major cleanup because of that. I only keep artists I like a lot, and friends. Else it is really hard to keep with your updates. :<
The most annoying thing is when people are not bulk updating some stuff. It's nice if someone is being productive and doing 10 (for example ) quick chibi or sketches everyday but when you upload better combine them and submit one deviation than uploading them one by one >.> But yeah as others already told it is different story for completed works.
For me though, 1 deviation per week or even rarer it would be perfect, LOL. For sure I would have more time to look at each piece and comment properly (..maybe. haha, now I'm master of fav & run XD)