I should but mixing climbing/rowing/calisthenics I just don't have enough time to rest and relax.
I mostly try to add some flexibility excersices at the end of my routine, depending on my current goal.
For example, I'm trying to achieve a press to handstand, I know I need more hamstring flexibility for that, so I do some pancake stretching. Like 3 sets of 30s with some weight added.
I usually do 2 or 3 of these complementary stuff.