You are going to get Jammed for the bill. Part A is automatic and is for long term care as far as I am aware, part B is for direct medical care. IMO, that 140 per month is not worth the risk these days, anything can happen in a second, and although you might be ok with the VA, they may not have the means to get you through what life can throw at you and the bill can be steep and 140 per month is very cheap piece of mind.
Your life, your money, your call.