Been training since the mid 80's.  I change routines around here and there.  No longer need to go super heavy.   Currently doing full body workouts M/W/F which has me in and out of the gym in about an hour.  
Same here.  I started lifting three days a week, doing cardio three.  I do legs or running in the morning, upper body or other cardio after work.  Evening workout wakes me up after a day of sitting at a desk (or standing).
Like many others, i be become increasingly instinctual over time.  I pretty much always do the same exercises, but reps and sets are never the same.  I back off and push on as I feel -- no longer forceyslef to get X reps or sets if its feeling bad.
I feel a lot better this way.  Before, I would always ignore pains and try to tough it out.  In the end, though, that approach just led me to ignore my body's feedback... I got lost.
Once I started adjusting things based on how I felt instead of blindly 'soldiering on' and trying to hold myself to a 'rational' plan, I finally started feeling pretty good about my workouts.  Well, for the past year or so anyway...