Developing a warm-up routine to ensure you practice a variety of different areas in one ‘routine’ is a great idea.
This warm-up routine could be 15, 30 or 45 minutes - depending on how much time you have!
It is especially important if you are only playing the bass clarinet infrequently - a good quality 15 minute warm-up on bass clarinet as part of your practice routine will keep you in shape.
I recommend that you create your own routine to include the following aspects:
Long tones/air warm-up exercises: to switch on your diaphragm support & embouchure. You could use a drone for this aspect of the warm-up, to also tie in intonation (hitting two birds with one stone!).
Exercises to warm-up the fingers: scales or other patterns.
Exercises to warm up your tongue: scales with tonguing/a variety of different articulations. Varying articulation patterns. Fast tonguing practice.
Over the break: warming up over the break, slurred & slowly.
Altissimo: the biggest problem with altissimo, is that we don’t use it all the time - meaning that it will always be weaker than the rest of the instrument. Incorporating a tiny bit of altissimo into your warm-up routine is the key to mastering it! It could be something as simple as extending your scales to the altissimo range.