Fun & Fitness over 50

In more ways than one! Yes, we are experiencing some hot and humid weather here in the northeast but "The Heat Is On" is also the name of one of the training rides in Edwards' and Reeds' The Heart Rate Monitor Book for Indoor and Outdoor Cyclists.
I'm trying to get back in a training mode although I'm not sure what I'm training for. I don't really have a goal for the rest of the year after completing the 100k and 75 mile charity rides.
I originally set a goal for completing a century by fall but I'm hesitant to commit to one as my job situation is still not settled.
Also I feel I need to make some adjustments for comfort before doing a century and that will cost me money that I don't have right now; namely a better pair of shorts or tights with a better chamois and a better seat. A bike fit would be nice too.
In addition, I had a back spasm just before the 75 miler and am still feeling the repercussions of that especially on rides with a lot of climbing.
Anyhow, I would at least like to get faster and improve my climbing so if you can call that a goal, as vague as it is, I guess that's it.
With that end in mind, this ride is part of their "strength spoke" on the "training wheel".
The instructions were to accelerate as hard as you can for 10 seconds and then recover and do 5 to 8 sets of that. The alternative approach, which I did, is to ride in rolling terrain and charge up short hills without downshifting or reducing cadence. Then on long hills, shift into a harder gear halfway up, stand and power over the top. The only thing was, I forgot about recovering in between until about halfway through so it was probably a harder workout than intended.
So I guess I'll keep working on strength and climbing for awhile then start mixing in some speed work.