We actually haven't been working on it that long, we've just been working on it very publicly. We've spent a bit more than 2 years on it so far, and have been open beta for a year. Most publisher developed games are worked on for 2-3 years (or 10 if you're Blizzard) before being put in the public's hands, but since we're such a small team we can't develop the game in isolation. We use the playerbase for design ideas, testers, and everything else.
Beta is even a fuzzy term. For us, it means we still want to add some major features and eliminate a lot of bugs before we call it 1.0. But every team has their own standards--I think AirMech stands up really well compared to a lot of games that are out of beta, especially when you look at micro-teams.
We don't wipe or reset accounts for normal play or even minor exploits (though exploits through hacking we do contain so they don't wreck the economy). So many of the old players are "rich" with things they have gained, or just XP and Kudos amounts. Since you gain no gameplay advantage for being high level and having all the "things", we see no reason to reset or wipe. It's our way of saying thanks to people for growing the game up with us. :)