Of course, at any time. Again - log in to cPanel (see how HERE) and go to the FTP Accounts icon.
More or less in the middle of the page (sometimes you need to scroll down the page) you will find a table with FTP accounts already set up.
As you can see, you can change the password, change the account limit and remove it completely. When you click change the limit - the system will show you the current value and allow you to change it.