Years ago, I used "the + extension" with Gmail for practically every site and every account I created. (Of course, also before "Sign in with Google" became ubiquitous.)

This was only manageable because I was already using a password manager app. And so with every service, I'd need to scrounge up the email address I'd made up for it, along with the password. Not always easy or straightforward. Also, when calling Customer Service, the first thing they asked: "What's your email address?" and I would need to do exactly the same scrounging, just to tell them the right answer.

So I eventually abandoned "the + extension" and I nearly stopped using "alternate email addresses" and I standardized on one singular email address for practically every account. This has made lookups much, much easier.

However, I did use it as recently as 2021, and it served to notify me of exactly where a particular flood of spamming and phishing came from. I used it once for an "Echovita" service and they subsequently had a massive data leak. I still get Echovita-related spams and phishing emails. But I can always tell them apart, because they are perpetually addressed to <[email protected]>