The rules aren't based on time, but basically on diversity of shareholders (there need to be a lot of shareholders and a lot of shares outstanding) which makes sense.
You need 7m publicly held shares outstanding (many IPOs don't do this, a lot of shares are controlled by underwriters and insiders who can't sell at the IPO) at least 2,000 shareholders and some minimum trade volume. There's a minimum share price too, but that doesn't effect IPOs.
CBOE probably has them, or possibly through your broker, but they handle compliance so the nuance of the rules isn't terribly important (if you can buy or sell options for a security through your broker they have already met the standard).
The numbers I mentioned are in the Federal Register, but quite a while ago. The numbers are still current, though other parts may have changed:
You need 7m publicly held shares outstanding (many IPOs don't do this, a lot of shares are controlled by underwriters and insiders who can't sell at the IPO) at least 2,000 shareholders and some minimum trade volume. There's a minimum share price too, but that doesn't effect IPOs.