I am tired of typing my password to add new packages with Synaptic.

One solution is to edit the sudoers list with sudo visudo. To automate the sudo password for all programs add:

%yourgroup ALL = NOPASSWD: ALL

But this is excessive, so to automate the password for just a particular program provide its path like this:

%yourgroup ALL = NOPASSWD: /usr/sbin/synaptic

Now I can add new packages with Synaptic without being prompted for a password.