Your pose made me chuckle. My first thought was that 10 miles is as far as you can swim!
Although twin motors may offer some extra sense of security, the weather and sea conditions have more to do with your range than twin or single motors.
Where would you prefer to get stuck; 3 miles out in 30 plus winds and 6 foot seas, or 30 miles out in calm seas?
Depending on the sea conditions you may not be able with one motor to get back.
Make sure you plan for the worst case ( well bad case) scenario. Can you signal for help (VHF, EPIRB, etc) can you survive if the boat sinks?
In reality, there are times when you shouldn't leave the dock