How can I opt out of the iPadOS 18 update?

If your iPad is capable of update to iPadOS 18.x, your only available update path is now to iPadOS 18.2.

With release of iPadOS 18.2, only iPad models with iPadOS 17.x installed that explicitly do not support iPadOS 18 can be updated with iPadOS 17 "point updates".

You don't have to update your iPad if you prefer not to do so - but will not benefit from any essential security updates or new/fixed software features. Be aware that the red available update badge can only be suppressed by installing the available update.

Speaking solely of personal experience with an iPad Pro, I have not encountered any significant issues with iPadOS 18.2.

iPad Pro M1, currently running iPadOS 18.2.

Speaking of personal experience, my iPad's battery endurance has actually improved following update to iPadOS 18.x - and is typically 7-9 hours from a full charge.

Being my primary computer of choice, I use my iPad heavily throughout the day.

Depending upon Apps and screen brightness, 8-15% battery utilisation per hour of use is entirely normal. Your indicated usage is well within the realm of reasonable expectation.

Likewise, your iPad can be expected to become warm with normal use. High screen brightness and CPU-intensive tasks will produce more heat - heat being entirely expected of any electronic device. While your iPad can be expected to become warm (or very warm), it should not become uncomfortably hot to handle.