Is there a way to archive emails so I do not have to waste storage capacity?

Firefox has no email features. Email accessed through Firefox will be web based email, any options including archiving will be part of the web based email service. You will need to contact the support for the email service that you are using to see if they have an archive option. It may require using POP3 access if the email service supports it and using an email program to download the emails to your computer.

Thanks Tony