yes it can cost you if you miss a purchase by using a limit order that doesn't execute.

FWIW, I never let a given limit sit for more than a minute before moving it, and rarely even that long, so that's not really an issue. I'm just trying to see where the bot on the other side will trade. It's usually a bot, whether it has a bid in already or not.

On rare occasion you can outsmart them, for very thinly traded stuff. You put in a bid, the ask moves away from you. You move your bid up, the ask moves up the same amount. This happens a few times and you s see the pattern--now your bid is above its original ask! So, you cancel your bid. Wait a short while, and generally the original low ask comes back. You pounce on that price (still a limit order). Often you'll get the fill there. Nobody will get rich this way, most of the bots are too smart now, but it's entertaining.

Jim