In my humble opinion only, you are absolutely going to want a 500kwh model. I can cover these distances (up to 60 or so) dependably on flattish terrain on my ToughRoad, but that is with the 500. The crushed stone surface really adds a lot of drag also, which is a range killer. A nice feature of the Yamaha system is the lack of appreciable drag when riding with the power off, which you can do across flats easily at least on a paved rail trail... it really adds to your range. But if you're out riding by yourself, like I usually am, you tend to ride faster than if you're just tooling along with a friend, and that impacts range also.
The last time I rode with a couple of friends on a gravel trail through the woods we went twenty some odd miles and I think I used maybe five percent of my battery. If it's just me it would look more like twenty percent, because I would have be in Eco all the way and be going a heck of a lot quicker.
If your favorite distance is 50 or higher, 400 won't get it. You'll be a nervous wreck from watching the range all day. My own favorite distance is 30 - 35 which is nothing, even if I go in Normal (middle range) mode the whole way. My last bike had a 400kwh battery and I would never have attempted to go that far without the charger in a pannier on the back. Big part of why I got this one!
