[passivate]

Not the OP, but I would turn it off simply to conserve battery life. I'm still rocking a 6s, and my phone gets slower and doesn't last as long with every update.

Don't get me wrong, I appreciate the updates, but I'd also like to maximize the battery life.

[astrange]

It doesn't use any battery life compared to turning the screen on.

[danShumway]

But do you leave your phone's screen turned on 24x7?

I buy that there are more expensive things you can do with your phone, but even if turning off Bluetooth is only giving you back a small percentage of your total battery usage, that might genuinely be noticeable on an older device with an older battery.

[astrange]

I would say it's doubtful it even uses 1% of it. You can use low battery mode to more intentionally extend it.