Your Gmail can be used over and over again, with no one the wiser.
You can append to your existing e-mail address in various ways, and this could be pretty useful for seeing who leaked your e-mail address to spammers. For example, for your bank, give them the address myaddress+banking@gamil.com. Then, if spammers send to that address, you can quickly see where they got the e-mail address from!
I’ve tested it with Proton Mail, and it works in exactly the same way.
if you’re self-hosting your own e-mail with postfix, you can do this as well: https://www.postfix.org/postconf.5.html#recipient_delimiter