Yes, the rockies can be troublesome. I fly from Pearson Filed (KVUO) to Ogden, UT (KOGD) for fuel (534 NM about 4hrs) I keep the freeway off my left wingtip most of the way, and will cut south of Laramie, WY to get to Fort Collins, CO. 400 NM about 3 hours). My flight will be about 900 NM.