I know personally I could stretch more, and need to even more so now that I have started going back to my martial arts school.
So the question is how much is enough to affect change? Studies show that stretching four times a week for thirty seconds per body part will yield flexibility improvements. it is not conclusive as to whether more that four days if helpful.
That being said my personal mission will be to shoot for four days a week. I do tend to focus more on the lower body due to the extreme flexibility needed for my martial arts pursuits. My toughest/tightest area are my hips, more specifically the lotus position/stretch. The flexibility of my legs is actually fairly good and I have no problems with high kicks, but the lotus position is the bane of my existence.
Here is the lower body stretch routine that I am currently following:
Day 1: Holding all for at least 30 seconds
Standing piriformis stretch on a raise platform – 3x each side
Lotus stretch – 3x each side
Front Split – 3x each direction
Straddle Split – 5x
Day 2: Holding all for at least 30 seconds
Standing piriformis stretch on a raise platform – 3x each side
Lotus stretch – 3x each side
Hamstring stretch on bar (I like to use the smith machine and raise the bar each time)
From this position I roll into a side kick/round house kick position – both positions 3x each side
Leg stretch machine – 5x
Here also is a link for a very thorough full body stretch routine, you may not need all listed but all body parts are covered.
https://jettllc.biz/wp-content/uploads/2014/11/stretch_routine.pdf
Good luck stretching!!