A round trip 8 day route from Boston exploring New Hampshire, Vermont, & Maine. There are lots of stops and scenic sights to enjoy the natural beauty in early fall! This is a moderate paced itinerary which I would recommend spending
Leaf-peeping has become super popular and lots of the charming boutique B&Bs book out quickly because they are small. A few of the areas book out completely by mid-January. I would book no later than February.
There are also many foliage maps which will help you determine when is best to plan your trip. It is not an exact science as many things affect the exact timing of "peak" including rain fall, temperature, and more. This is my favorite map for New England: https://newengland.com/foliage/foliage/peak-fall-foliage-map/