I'm curious what your elevation change is over the 8 miles. After most of my year commuting in Boston and then 3 months in NYC I'm now commuting in the Berkshires. About 1/2 way into it I have a brutal 2 mile dirt road climb with a gain of about 1100'. I could go another route and stretch out some of the climbing over more miles but I'm liking the challenge. Unfortunately, it's so steep and the road is so rough in parts coming down that I can't really take advantage and descend at too much speed.

I can do this for a couple of months but I'm not doing it every day- only 3-4 x's per week and year round I think it would grind me down. My wimpy flat commute back in Boston is 5 miles shorter each way and has an elevation shift of about 80' over ten miles. Hilly commutes can be tough for sure. 8 miles with a steady uphill is a ton of work every day. You will sure get stronger from it.