I started riding because my husband started riding because our son started riding and racing. It took me about 2-3 years before I "consented" to let my husband set up his old mtb for me and buy me my first pair of shorts and a jersey. My first ride was about 6 miles and he had to push me up a small hill with the back of his hand...
I thought I was fit, after many years of aerobics and gym activities, but i had slacked off a bit and had gained weight. My husband was very patient with me. I got a road bike after 2 years and now we pretty much ride together all of the time. What happened was that I got much faster and confident and he doesn't feel the need to hammer all of the time. Sure, i will never be as strong as he is, but he does his faster rides when he commutes to work. So he'll average around 17-17.5 when he's alone and when we ride together, our average will be anywhere between 14.5 and 16.5, depending on terrain and how we feel. I don't think I would want to be out riding for 2-3 hours at a time and leave my husband at home. Riding is pretty much our whole lifestyle and almost everything we do revolves around it. Some of our friends think we're "over the top" because we're together so much, but this is the way it is...