I'm 72 all you young pups out there!

About 20 years ago I self-taught chords and barr chords and learned to strum maybe 20-30 songs but it kind of got repetetive and boring and I quit maybe three years ago. So I decided to start from scratch and am now on Basics 2 learning scales. I'm wondering at what point do I stop and move on. What is the level of proficiency that is reasonable before moving on? Like being able to keep up with a metronome set at 100BPM? And then I notice when I learn a new scale, I kind of get hosed up trhing to remember the first one..Any tips?

Also, I wanted to share with those who are learning chords and chord changes that a metronome was essential to me and my progress. So if a particular chord change was giving me problems, first I would just deliberately move from one to the other and back, watching for any tension in my hand or arm and focusing on relaxing it. Then I would set the metronome for maybe 40bpm and go back and forth. When I was able to do that consistently I would crank up the metronome 5 -10bpm and continue until I could do 120bpm. I was amazed at how much quicker I could master a chord transition.