Thanks for sharing your thoughts everyone.
Right now I'm less interested in training to complete an event, like a Brevet, and more interested in riding longer in a day simply because I love riding my bike. My routine has been to get an early start and then get home by such and such a time because of a family commitment or whatever. I'm now having more opportunities for longer days on the bike without the time constraint. I believe the key, for me, will be many short breaks (with some light stretching on each break, in addition to checking out sights and having a snack or whatever). It's managing the older issues I've had with my body, not solely caused by cycling, that worry me the most. I'm not concerned that my legs or lungs can't handle the distances, it's the contact points. I'm also not concerned with speed and as I think it through with input above, it's not about riding slower per say, but riding at whatever pace feels right and stopping more frequently and perhaps for a little longer than my usual micro-breaks. I'm hoping that will allow me to add in rides where I go from say 4hr riding time to 5 or 6 or a little longer, and still feel close to how I do after 4 hours (which is pretty good).
And for those Canadian's out there, like moi, Happy Canada Day for tomorrow!