Papa Tom, I think part of the problem your running into here is the name of the trail. There are two related trails - the "Farmington River Trail" and the "Farmington Canal Trail" and the trailheads for each are roughly half a block from each other. I live in Farmington and even locals get the names of them confused! You ask about the River trail and bktourer1's reply is about the Canal trail!

The Canal trail is flatter and much longer than the River trail. The Canal trail is the one that runs to Massachusetts. It is indeed 25 miles from the town of Farmington, CT to Southwick, MA along the Canal trail. I've ridden to the state line (but not all the way to Southwick) and it's not too hard at all. The water stop that bktourer1 mentions is not always open (summer only?) but there are places where you can easily access a convenience store or a small grocery store from the trail.

The River trail is roughly 15 1/2 miles from Farmington to Simsbury, where it meets up with the Canal trail. Some of the northern portion of this route is on public roads through Canton and West Simsbury. Other parts of this trail are newly constructed and I haven't yet ridden them. The River trail is more scenic (in my opinion) because it has nicer river views through Unionville and Collinsville. Also, Collinsville is quite a nice little town with a couple of good dining options. The negative side is that the surface of the trail is somewhat disturbed by roots growing under the asphalt surface in and around the Burlington section - not a deal-breaker in my opinion but kind of annoying for a mile or two. I ride it with 700c x 28 tires so maybe it's not so bad with something wider.

Your idea for a trip sounds great! Farmington is an old town (1645), so we have historical sites, museums, etc. Collinsville has the restaurant options I mentioned and a pretty big antique store in the old mill. I also like to rent canoes and kayaks there.

Hope I've been of some help. Have a good trip!