I find it's just like running. The more hill rides and long distance rides I do, the better my average speed on the shorter rides is. Just keep riding. I've been trying to catch my husband for year's. Unfortunately, he is increasing in fitness as fast as me!
"Well-behaved women seldom make history." --Laurel Thatcher Ulrich
'09 Trek WSD 2.1 with a Brooks B-68 saddle
'11 Trek WSD Madone 5.2 with Brooks B-17