In other words, don't stick that etchant tray back into the kitchen cupboard. The etching should take 5 to 20 minutes depending on board size. If it takes much longer, the etchant may have dissolved its fill of copper, and should be disposed of properly. Clean Up Restore the etchant to its sealed plastic container. Wash all the parts, trays, and circuit boards with plenty of fresh water.
Some people like to drill the holes before etching.
I prefer to etch first to allow the etchant to carve starting center holes. The holes tend to guide the drill bit to the center of the via. I used my Dremel drill press at low speed. I broke three bits. I guess I was supposed to use it at high speed and also prevent the board from shifting.