For me it depends a great deal on the route the characters are taking. If they're traveling three days through settled and patrolled farmland I'll say "Is anyone doing anything special while you travel? Okay, you travel 3 days, stopping at modests inns overnight (take off 5 gp each). About 4 pm of the third day you arrive at Glockenspock weary from your travels."
In a more interesting environment I may have something happen every few hours. Frex, the characters were crossing a very dangerous desert to raid a gold-mining camp. It took three sessions just to get there, and plenty happened along the way. I got a lot of use out of the Wilderness Survival Guide on that one.
Most often I will primarily describe transitions, such as bridges, terrain changes, towns, interesting people, and mischances (out of food, horse goes lame, etc) Most of these are quickly over, but I throw enough in so that when I'm providing a significant encounter it's not immediately obvious.
All of this works pretty well for me, but it doesn't entirely solve the issues mentioned by the OP. I'm hoping someone posts some more good ideas.