I dont like to enter it either that one time, but it is better than every time and its is better to do it one time and have it secure then to have someone get your info from your browser and get into your site. Security is not always easy, but it is "always" important and worth a little inconvenience.
Did you know that many times the weakest part of any connection is the browser, think about that before you go storing your passwords and such..
However if you must, at least dont use your cPanel login. You might be interested in this.
http://docs.oxwall.org/faq:how-to-add-new-ftp-account-to-update-add-plugins-and-themes