For running my personal preference is working on speed and then distance, so i set a target pace for 2 miles and once i get it and am able to consistently reach that goal with reduced effort i start working on my 3 mile pace, reach my target and then go to 4 miles. I think i just enjoy shorter faster runs than longer slower ones.

Wasn't sure if this would work for cycling and especially over a 100 miles, or even what approach i should take. Is there a good way to build speed over a long distance (100 miles)? Would intervals work for a century, seems they may be better suited for crits or tri speed work.

If i do go with the speed work, should i use the same approach? Set a goal pace for say 20 miles, reach it then start working on a 40 mile goal pace, and so on until i can do 100 miles (this is what i've been doing).