I think it’s whatever you can commit to consistently. It might be a 3-minute warmup when you get out of bed, or a consistent longer stretching routine.
Well, for your warming up you need 15minutes hard training for a really good stretching. (5minutes is also possible but it has to be heavy) en for your stretching is 10-15 minutes great! But longer is better! If you just have 5minutes just chose 3stretches en do this on your time.
For stretching I prefer yoga exercises. They are great! They really make your body flexible and grace. It usually takes me 15 minutes to stretch at least. As more as better
I think from my personal experience. Morning stretch is the best time. And yoh have to do for about 15-30 minutes of stretching, yoga and pranayama to get maximum benefits.
I usually wake up at 10 am or earlier, or some times at 11:00 am. But i always think strecthing is good for you at whatever time you wake up. I do intermittent fasting and workout as well so i stretch before and after i finish. Stretching doesn't need a time or place to do it, just do it when you can and you'll feel good after for sure.
If you mean how long to hold each stretch for – to have any significant impact hold a stretch for minimum of 10 seconds and maximum of 60 seconds as it states in the book Ultimate guide to stretching and flexibility by Brad Walker.