Driving a Chevy Volt (with an 18 kWh battery) makes you very aware of the different fuel-costs of different routes -- I very often have a choice of driving "over" or "around" small mountains (~hundreds of feet of elevation change, not ~thousands), and you can easily see the battery drop as you go up, up, up and it doesn't always recover much going down, down, down.
Going up and down mountains should be mostly a wash, apart from these small losses.
What's really eating into your battery in a way you can't recover with regenerative breaking ever is wind resistance.
Routes that make you drive faster for longer cost more energy. (And given the way wind resistance works, for the same average speed, a variable speed is more expensive than a constant one.)
Optimal regenerative braking recovers like 2/3 of the energy lost, and suboptimal braking -- for instance, if you need to decelerate more rapidly because of a bend in the road -- is worse.
Every 100 feet of elevation change amounts to ~1% of the battery capacity of a Chevy Volt; a couple of small mountains, with lots of ups and downs, and it's easy to lose 5-10% of your range versus taking a more level route, 5% if you brake well, 10% if you brake poorly.
[Which is not to say that hitting the thruway doesn't also kill your range fast.]
