Must I have a business banking account for an LLC that has never done business? I may use the LLC and domain in the future, so pay the annual fees to maintain them.

I set up an LLC in Feb 2018, using LegalZoom. In parallel, I registered a web domain corresponding to the company name. It was all done very quickly, and I used my personal checking account. 

Yet I never did any business. The LLC has sat for a year, untouched. 

I want to keep the LLC registered and the domain active, in the event I use the LLC as a business in the future. Those require annual fees. 

Must I maintain a business banking account for these annual fees? Or can I continue to use personal accounts, and just keep good records?  That way if I start doing business, I can set up a business account and transfer the exact money spent on start-up and maintenance fees.