Nothing to worry about, Its safe, But anything can go wrong anytime. so you always have to be sure
Secondly, i dont think you require to update bios whenever you install a new win... I mean whats the need? to update bios everytime. Unlike Windows, your bios not stored in Hard disk, its stored in the motherboard memory, if you format your hard disk, your bios still remains in the motherboard.
Rest details you can read in following link, its just a one pager article regarding all important things for bios
HTG Explains: Do You Need to Update Your Computer’s BIOS?