Do COBRA regulations specify how long an employee must be on their specific group plan before becoming eligible for COBRA? Or is this determined by individual states? Is the COBRA benefit only available for 18 months?

To the extent of my knowledge, COBRA is available for a maximum of 18 months. I'm not sure how long you have to be on the group plan before being eligible.

My understanding it is available to anyone insured under a group plan, I did not see a time frame, the only limits is as to the length of time you can be under cobra.

Of course Cobra is very expensive, and most people can't afford it anyway.

Have you been refused coverage ?

I think once you have been on it it does not matter how long you have been insured. We just went on COBRA and we have to pay for the entire month up front. If we don't then my husband will not get the operation he needs. I thought we would have to pay week to week, so be prepared.