That's an interesting question.

You've done lesson 2 so I don't think there's any real reason that you shouldn't be doing texture analysis as part of your warm up routine. Personally I don't use textures as a warmup because they encourage me to use my wrist and I like to get my whole arm moving during warmup time, plus I don't get very much texture done in 5 minutes. That's just my personal preference though.

Reading between the lines in your post, you're saying that you do textures as a warm up "fairly often" but are "not confident in my progress" makes me think that you'd like to be practicing textures, but feel hamstrung by the time constraints of doing them during warmups. Textures take a long time, so I don't think you should be expecting a lot of progress during a warm up time window.

If you're interested in doing textures, why not start collating your efforts into the 25 rows needed to complete the challenge? If you check out the challenge page https://drawabox.com/lesson/25textures Comfy recommends doing the challenge slowly, alongside the other lessons anyway. Then when you're done you can submit for official feedback. You can chip away at it in little little chunks, like you're doing already, or perhaps set aside one day a week to textures to really settle into your flow and make progress with it.

That's just my opinion, anyway. Good luck.