Biking around Lake Tahoe took me about 4 on-bike hours, and a little under five hours total. The highway on the Nevada side is reduced to one lane at times for construction, and sometimes the delays reach 20 minutes, as I discovered when I was leaving town on 50. On the bike, though, the most I waited was about five.
The round trip was just over 70 miles, but at 6500 to over 7000 feet of elevation. The flat sections were well paved, save for one area near Incline Village, and the speed was quick. Anytime I tried to work a little harder, such as climbing out of the valley, I couldn't hack it. Too much time near the ocean, not enough time in the mountains, perhaps.