My First Alliance imploded 6 hours after I joined it. The corp itself exploded 22 days later.
My second alliance didn't explode for 3 months, and the corp limped on for another couple of months after that
My third alliance lived for about a year, but I left before it "intentionally closed the doors while all the corps joined a different alliance" - the corp is still going.
Now I've been in the same alliance for more than a year, and it hasn't esploded... yet.
Welcome to Backstage!