I'm doing around 350 - 500km+ per week with 2 rest days so 3hr+ rides are 2-3x a week. No time constraints, I'm semi-retired (51) and just need my phone with me to sort out any issues that might arise. I do 1 or 2 hard rides a week, a medium effort or two and 2 easy/recovery rides, typically.
I did a 3hr ride today. Last week 2, the week before 3. One, sometimes two of the longer rides are with others; Club ride or training group. HIIT days are always short.
My wife say's I'm basically living like a Pro now
. I often train with top local riders of all age categories, some of them aspirant Pro's and a couple of Pro's who are waiting to get back to their normal routines.