if you are indeed the only person ever to have access to your Mac, you might ommit the admin password.
This only goes as long as you do not connect your Mac to the Internet.
Using a zero length admin password while being online is at least unwise if not outright dangerous.
Hope this helps,
Apple and others state that running with a blank password is tantamount to leaving the barn door open. Additionally, you'll not be able to do some things, such as install software or run the Terminal app. Use passwords (upgrade your short-, medium-, and long-term memory abilities, so you'll not forget them) and exercise otherwise sound procedures. Although not the latest, DL, and read Apple's Security Guidelines.