I’ve been quite lucky with battery life so far. Always run my bus powered Keylab II 88 and Focusrite 4i4 just fine from MacBook on battery. Seems to last several hours on one charge. I always have a charger with me just in case, but prefer to not be connected to a power outlet I don’t know.
If the gig file loading time is a concern, you could always create separate gigs for each set?
There is no way I would perform live if I only had to rely on the battery. I always have my MacBook connected to my uninterruptible power supply (UPS).
I could look it up, but I think it’s just the nature of the Lenovo laptop with these new Intel chips. Basically I think it’s meant to be plugged in when used, which is fine with me.
I found an app called Twomon SE that does the same thing (streaming my Windows laptop to my iPad) for far less. The computer app is free, the iPad app was the cost of a footlong sub from Subway. Works great over USB