So I bought a bike.
A steel bike. A heavier bike than the one I was riding. Technically, a "cyclocross bike", but most people, including me, buy it to use for "light touring".
The very first day I bought it, I took it camping. I rode with a group (on mostly dirt roads) about 30 miles to the campsite, with all my gear on the back. We camped overnight, and then packed up and rode home in the morning. It was awesome. The bike came with 700cx 28mm randonneur tires, which were a bit narrow and lightly treaded for all the dirt roads, but definitely way better than my road bike. I ordered some 32mm knobbier ones for the future. With all the weight I had loaded on the back end, and the narrow tires (pumped too high too!), and the dirt roads, I definitely had my some skidding issues and had to be cautious with turns.
I had a really good time and definitely want to do it again. With the dirt roads, hills, and all the weight on the back my speed wasn't very high, but it was definitely a lot of work. I was sore for a few days after. I think that doing this type of riding will still translate to speed on the bike at triathlons. I'll be used to carrying more weight and fighting more resistance, so riding my lighter bike at a race should feel easier, and my legs should eventually get stronger.
Since getting my new bike I've also started commuting to work a lot more. The steel frame absorbs the road vibrations a lot better than my still aluminum road bike, and makes traveling on Michigan potholed roads and sidewalks a lot more enjoyable. It's only 4-6 miles to get there (depending which way I go), so ~10 miles round trip 3-5 days a week really adds up my biking mileage. I usually have a hard time getting bike mileage in since I don't really enjoy it, so I'm hoping these little stints will improve my cycling fitness gradually. Some of the rides are quite leisurely, but pretty much any hill involves work. I'm trying to get Justin to get a bike so we can do some leisure rides together. Until then, I let him ride my new bike (it has flat pedals on one side, so he doesn't need cleated shoes), while I ride my road bike, and we can go on mini-adventures together. So far, one picnic is in the bag. Hopefully, many more to follow.