Do You Plan Your YouTube Video Length Before Recording Or Go With The Flow?

I am curious what your process is for deciding video length before recording. Do you pre-plan your videos length or do you go with the flow? For me I LOVE making videos for my main at around 10 mins long, I feel that its short enough to keep peoples attention and long enough to not be ridiculously short. I do find longer ones perform better though with a lot higher average percentage viewed than usual. What's your take on this? I always try and pre-plan in my head roughly how long the video will be. Tonight I am recording one for my YouTube and I am going to aim for about 10-15 mins.