I never create a new document in Illustrator from scratch. I use a template — a regular .ait file with preset settings. When saving, Illustrator asks for a new filename. Templates can include units, bleed, guides, swatches, artboard color, and more.
I have many templates for common paper sizes because I work with print regularly. My base template is empty because Illustrator’s default new document loads swatches, brushes, symbols, and other clutter I do not need.
Using templates where possible simplifies work and avoids repetitive setup. Use templates!
PS^ Attached is my old business card template with my preferred size, tested icons that print well, and swatches for bronze, silver, and foil-gradient inks.