It is never too late to purchase higher amounts of car insurance. New Mexico requires all vehicles to be insured up to $25,000 per person and $50,000 per accident. What this means is that if you are seriously injured in a car wreck with a minimally insured driver, a potential recovery is limited to only $25,000.
Therefore, you benefit from purchasing underinsured motorist coverage (UIM).
A purchase of minimal limits bodily injury and UIM will not benefit you because of obscure New Mexico law that allows the insurance company to subtract the amount you receive from a negligent driver. For example, if you broke your arm and leg and incurred over $50,000 in medical bills you could only recover the $25,000 from the person that hit you and, because of New Mexico law, your insurance company would not provide you with the UIM coverage to pay for the remaining $25,000 in medical bills.
This is commonly known as an offset and you should purchase the highest amounts of bodily injury and uninsured/underinsured motorist you are financially capable of.