I just looked at the data for my ride from work to home.  It is 16.8  
miles, with 1558 feet in elevation gained (an average of 1.76 percent  
grade for the entire distance).  It took me one hour, 32 minutes.  I had  
an average HR of 161, with a highest HR of 180 (my max is about 186).  66  
percent of the time was spent at a HR of 160 or above (160 = 86% of my max  
HR).  27% of the time was spent at a HR of 170 or above (170 = 91.4 % of  
my max HR).  (Whoa!  I thought it was hard, but that's a long time -- 25  
minutes -- at a high HR.)  It's a very hard ride, with three hills where I  
have to be in my easiest gear and stand on the pedals.  One hill, I almost  
stopped and walked up, which I haven't done in years.

I'm currently eating low carb, and it'll be interesting to see what types  
of changes in diet I make this year in order to keep biking such hills.  
Currently, I'm riding from work to home one day per week; from home to  
work (fewer hills) one day per week; and one long ride, with 20 miles of  
nothing but hills then as many miles as I can fit into the time with some  
hills.  I'd like to either ride into work then back two days a week or  
extend one or both of my rides to/from work.  Last year, I upped the fruit  
level (currently, only berries every once in a while) to have a few more  
carbs.  I also ate some carbs/protein during long (typically, 40+ miles)  
rides.  The previous year, I was convinced I "had" to have pancakes after  
my long rides.  Last year, I changed that, though there were some times I  
did have "higher" carbs.  I think I limited pancakes to some of the very  
long rides.