yeh itll depend on the individual plant and how quickly its growing but id say week three it should be pretty established.
thats my opinion anyway, ive had trouble overwatering in the past and i think its best to er on the side of caution. much easier to stunt a seedling with too much, and much harder to explain something like moisture levels to people who havent grown too much and have no reference. during all stages you never want anything getting bone dry but when wet it needs to be dry enough to allow some oxygen to get to the roots(within a few days). just gotta stick inbetween those confines at all stages but in the start since the plant takes up so little its much easier for it to just stay too wet so its best to lower the maximum moistness.... sounds like a bad porno.
for the first few weeks the seedling will be concentrating on establishing roots and dont need too much water. its kind of good to have them searching out for water instead of soaking in it. after that they kick off and get a canopy going.
stuff like perlite and vermiculite are put in soil mixes to aerate the soil and keep it from becoming too wet stuff like that will make it harder to overwater but still not impossible so itll depend on your mix and temps/setup how often youll need to water so its hard to be too specific. if youre bothered you should post up a journal, people pop in and catch stuff you miss yourself very handy for getting help and having all the info right there for people to look at when needed.
i would say water a small amount around the stem or let it soak up a little water from the bottom kind of keeping it half wet to semidry. i just water a certain part of the pot or not all parts of the pot atleast with a small amount of water so then there are still dry enough bits that will provide some air and even out the wet parts. misting is good but a little riskier on a first time (if its your first time)id say also in high intensity lighting watrer droplets will burn leaves and stress plants so only good if you are ok taking them out for a few hours or are using cfl or certain other types. once youve done it once youll know whats normal etc it gets much easier to figure things out.