Google, Microsoft, Apple, and many other companies manage many user accounts. Here's what they have to say about passwords and security, which is good advice for all.
"Choosing the same password for each of your online accounts is like using the same key to lock your home, car and office – if a criminal gains access to one, all of them are compromised. So don’t use the same password for an online newsletter as you do for your email or bank account. It may be less convenient, but picking multiple passwords keeps you safer."
"Passwords are the first line of defense against break-ins to your online accounts and computer, tablet, or phone. Strong passwords are phrases (or sentences) at least eight characters long (longer is better) that include at least three of the following: uppercase and lowercase letters, numerals, punctuation marks, and symbols."
"Apple policy requires you use strong passwords with your Apple ID. Your password must have 8 or more characters and include upper and lowercase letters, and at least one number. You can also add extra characters and punctuation marks to make your password even stronger. Using a strong password is the most important thing you can do to help keep your account secure."