Insurance - Collision premium versus car depreciation

"One rule of thumb: When the annual premium exceeds 10% of the car's value, drop it."
Via: http://twocents.lifehacker.com/if-your-car-is-old-you-might-be-wasting-money-on-insur-1585410417

Our car, in a private sale, probably would sell for around $5,500.

10% of $5,500 = $550

Collision: We currently pay $160 every six months ($320 annually for a $500 deductible, or 5.8%)...this means, if an accident totaled our car, the insurance company pays out $5,500 - $500, or $5,000. After $5,000 / $320 = 15 years, we would break even.

Comprehensive: We currently pay $22 every six months ($44 annually for a $250 deductible, or 0.08%)

Also:

""A good rule of thumb is if the cost of collision coverage is 25 percent of your vehicles value every six months, it is probably time to stop paying for collision coverage. Just think in two years time you have saved enough money to cover the cost of a total loss of your vehicle."

25% of $5,500 = $1,375

Collision: We currently pay $160 every six months ($320 annually for a $500 deductible, or 5.8%)