Hi @islush ,
It should be perfectly fine to leave them on, as the system has been designed for them, however it may be that the "light" from the keyboard may be disturbing to you at night.
You can if you wish ''dim'' the lights rather than turn them off. According to the [https://download.lenovo.com/consumer/mobiles_pub/yoga720-13ikb_yoga720-15ikb_ug_en_201702.pdf|User Guide] on p.4 it appears that the lights cycle through off - dim- bright -off when pressing the space bar (with Fn).
Hopefully this is of some help.