i can say from my experience, my levels were sticking at .25 forever up until just this week. my tank is about a month and a half old or so. i did a fishless cycle, without dosing anything. at about week 3 or 4, i added 2 clowns, who have done fine the whole time, and are still alive. from that point, i slowly added another fish until 2 weeks after i noticed that my nitrates were constantly 0. keep in mind, that my ammonia has always been .25 regardless of what i did. just last week, i added 3 more fish. again, my ammonia didnt change.
as long as fish are good, then any minor ammonia readings should be fine. like i said, ive had fish for the entirety that i have had .25 reading, and none are acting odd in any sense of the word.
i have come to a conclusion as to what has caused my ammonia though, even through the ammonia isnt creating issue for the fish, i have always been curious as to why i always have a reading in the tank when there shouldnt be. without going crazy in depth with stuff i wouldnt understand anyway, tap water can cause a chemical reaction, which caused ammonia. i didnt really believe that, since my water after i prepped it, was at 0. only until i add it to the tank, do i get a reading. the gentleman said there is a reaction that gets created when adding prepped tap water that causes it, so i decided to buy a rodi system to make my own. since then, my ammonia levels are 0, or next to zero. definately less than it was using normal tap water.
in any instance, if fish arent being effected by the amount of ammonia being seen, there isnt a worry to be had. the fish are the tell tale sign if there is a problem