So, 1 hour to the HTML 'tutorial' upgrade. Another upgrade is 1,000,000,000, according to the devs, pretty huge difference :/ You definitely need to add some late-game content, some system that requires players to keep spending their points not-on-upgrades (maybe you should consider some pvp system?)
We're adding in more upgrades that'll be released on Friday. We'll definitely see what we can do as a way of spending money instead of upgrades.