All good responses and points well-taken. ..

How would that advice come together for a weekly plan?

I'm 55. I can do a 40-mile group ride at 16 mph. I want to be able to do a 40-mile group ride at 17-18 mph. I probably have 12 hours a week to dedicate to it.

What would be the best use of that time for someone in that situation?

I can go on three 45-mile rides with groups that average 17+ and simply learn by doing and being pushed.

Or I can go on one 45-mile group ride like that and train on my own with a mix or shorter and longer rides.

What would you advise? I realize there are many ''depends'', but I'm looking for ''If I were you, I might try this each week and see how it goes.''

I