I very rarely see any of mine during lights on (occasionally on the vegetables), although they do become more active towards lights off. Also mention of Otocinclus being "naturally short-lived" isn't true, my oldest Otocinclus is at least 4 years old (and was adult when I bought it).
My oldest fish is an Otto which I bought in March 2011, so he's at least 5½ years old. I moved him to his new home today and he seems in good health although he keeps a low profile!