The decision to drive a distance to swing a coil depends on several factors, including the distance to the location, the likelihood of finding something valuable, and the cost and time involved in the trip.
As a basic formula, you can consider the following:
Expected Value of Findings - Cost of Trip - Opportunity Cost of Time >= 0
In other words, if the potential value of the findings (such as valuable items or historical artifacts) minus the cost of the trip (including gas, tolls, and other expenses) and the opportunity cost of your time (the value of what you could have done instead during that time) is greater than or equal to zero, then it may be worth the trip.
Regarding the balance between drive time and hunt time, it's generally a good idea to maximize your time actually searching for items rather than spending a lot of time on the road. So, if it takes an hour to get to a location and you plan to spend two hours searching, that may not be the most efficient use of your time, especially if there are closer locations that offer similar potential for findings. However, if the location is particularly promising or unique, it may still be worth the extra time and effort to get there. Ultimately, the decision should be based on a cost-benefit analysis and your personal priorities and preferences.