I think it definitely depends on your use-case. Like you wrote, if everything else you have open also churns through battery life, it's unlikely having Slack op

I think it definitely depends on your use-case. Like you wrote, if everything else you have open also churns through battery life, it's unlikely having Slack open will make a difference. However, if your other applications are a terminal, other efficient text editor (e.g. Sublime), and other generally respectful apps, I've found having Slack open is the difference between having enough battery life to work all day, and not.