Ask HN: What's a reasonable cash reserve to have for a bootstrapped startup?

I run a cash flow startup. We're profitable and I'm building a cash reserve. Yesterday I read that TINT [1] uses a "health ratio" of cash/monthly burn and theirs is like 1.6, meaning they have 1.6 months of cash reserve. To me that seems really low. I'm aiming for something like 12 months. Am I being too conservative? What do you guys have in your bank?

[1]http://www.tintup.com/blog/tough-times-dont-last-but-tough-startups-do/