While you haven't spent much time in RVs since the 70s I'd encourage you to do a lot of research on different models, focusing upon the size you might want to live in for extended periods. There is nothing wrong with comfort so be sure to consider what you might want to relax in, especially on those cold and/or rainy days. In our previous smaller 5th wheel we found that after taking out one of the uncomfortable fold-out couches and installing a couple of La-z-boys was the way to go. Removing a couch and putting in a lounge chair will give you more room too.
Depending upon what you might want to take along with you storage will be a premium. Make sure you have room for what you need and for things you like to do.
Also, since you'll be cooking don't overlook the fridge size and counter space for prepping your meals. Believe me, this will come in handy when you're eating at "home" 7 days a week. Of course, a small grill will help with cooking outside.
If you want to take a kayak or bike you can rig your tow vehicle (if you have a travel trailer) to haul both of those items fairly easily. In fact, if I was in your position I'd lean toward a pickup with a cap on it and tow a trail trailer in the 24'-28' range. The capper on the pickup can store a lot of stuff. A 3/4 ton pickup will cover any possibility that you might decide to go to a larger RV at a certain point. I like my diesel, but they cost more.
Research potential areas of the country where you'd like to spend your time. Now is a good time to follow the campgrounds forum for info on different parts of the country. I used to copy & paste certain comments from fellow forum members and put them into different Word documents titled by what areas of the country they best fit. I then used these to plot out some of our trips knowing some good campgrounds, sights to see, routes to travel, weather, etc. Plus it will give you something to do while contemplating your retirement. Then it will all happen before you know it. Enjoy this beautiful country. There is a lot to experience.
