I've always had a problem with buying games in alpha, playing the hell out of them, and then losing interest before they even officially come out. I played hundreds of hours of Minecraft only to stop playing entirely a few months before the 1.0 official release. I bought Kerbal Space Program, sent things into orbit, went to the moon, and had all sorts of fun, and now i've lost interest (Its even on steam and I can't bring myself to click on it.) I'm like an Alpha build gaming hipster, I liked games before they were feature-complete. My Starbound and Project Zomboid alpha purchases are looking bleak.
Are they adding enough stuff in the future that i'll be able to jump back in once I play through what's there? Is there a reason to go back and play regularly or will I build a prison and then forget about it?
Hopefully someone can give me an idea of whether or not I should buy in now or later.