If you don't use top-tier gasoline, you can put in a $5 bottle of Techron from Walmart once a month (assuming once in 1,000 miles, average driver).
The Math: As long as the top-tier gas is less than about ten cents per gallon more than the cheap gasoline, it's worth it to just use top-tier gasoline instead of hittin' the bottle (Techron; not Jack Daniels....).