Is it okay to keep my laptop charging at 99% all the time? Does it harm the battery?

It's actually pretty normal for modern laptops to stop charging at 99%. This is done to protect the battery, preventing it from going through constant topping off, which can wear it down over time. So, if you're leaving it plugged in, you shouldn't worry; it won't hurt the laptop. There are also battery settings in Windows and some brands like ASUS that keep it under 100% for longer life. If you want, you can check the settings in MyASUS or BIOS, but there’s no real need to stress about it unless you're keen on tweaking those settings.

Your battery might have lost a little bit of capacity, hence it seems like it can’t reach that last 1%. Keeping it plugged in all the time can definitely lead to more degradation. It's usually better for your battery's health to let it charge and discharge now and then. Most modern batteries have mechanisms to prevent overcharging, so don't worry too much about leaving it plugged in.

Setting the BIOS to 'always plugged in' is a good option and should help prevent any overcharging. As for your battery displaying 99%, that's pretty standard. As long as your BIOS settings are right, you should be good to go!

Your laptop might have a built-in setting that limits charging to 60 or 80% to help preserve battery life, especially if you keep it plugged in often. Check the settings on your Lenovo laptop to see if that's the case.

Batteries do have a natural degradation over time, no matter how you use them. If you’re mostly using your laptop plugged in, it’s not a big issue. But generally, it's better not to keep it charged all the time; just incidental usage while unplugged can really help with battery health!