I've read a plethora of forums and websites on this topic. It appears that many experienced and recent travelers do this and there is no problem, especially from France, Italy, Spain and Germany. Yet, I'm in no position to take a serious chance and I do want to come back here as a self employed person, possibly get a Visa when I go back to the States. I would love if I could go hang out in Croatia for a few days and come back here and have my visitor pass renewed another 90 days. Getting close to the deadline to change my air ticket and I need a definite answer. I have read the legit country websites and rules and...still, is this possible? I'm guessing between Schengen and Non-Schengen zones and I being an American, they will run my passport through the digital stamp? OR --> Since I'm renting an apartment here and living underground a bit...chance the stay until June (arrived Jan 1)and chance they won't notice or care about my over-stay. Not ideal, since I want to return.
Unlike the US, Schengen doesn't have the notion of your "90-day period," and there's never anything to "reset" at some threshold. The Schengen rules are that you may not be in the Schengen area for more than 90 days in any 180-day period without a long-stay visa. It doesn't matter how long your stays are or where you go in between; what matters is the total number of days you're there out of 180 days. If you just spent 90 straight days in the Schengen area, it doesn't matter where you go next, but you can't reenter for 90 days. The only legal way around this is a long-stay visa.
As for consequences: I can't speak to practical border enforcement, but in general it's best to not be breaking the law in the hopes that you don't get caught. Especially if you intend to apply for a long-stay visa later, they may well give more scrutiny to your travel record, and overstays can make them worry that you won't leave when your long-stay visa is up.