- non-legally speaking, consent for anything is never illimited in time. So whatever the law says, you're probably doing a dick move, I'm sure you can conceive that most people you're going to email would rather not get this email and you're planning to do it anyway. So if you act against these people's interest, don't be surprised if they react negatively (reporting the email as spam, complaining, reporting you to authorities)
- legally speaking... IANAL, but I don't think that you're correct that you have a legal basis to have kept this data, and even less to use it for marketing purposes. I don't think that you'd win the argument that the consent is still "informed" after many years of not hearing from you. If a reasonable person would no longer expect to hear from this company, then I don't think you still have consent under GDPR (could be wrong, IANAL)
Wait too long — respect people’s attention and time so much that you don’t send them anything unless it is ready and benefits them - and apparently it’s spam when you finally do contact them. Meanwhile, if you were just drip feeding them slop once a month, then you’re fine.
I happen to agree with the article author, the email ecosystem is totally broken, that’s far more of a problem than small teams who have well-meaning intentions and respect for their users’ time. You’re blaming the victim, rather than the email system that’s open to SPAM and dominated by gmail.
I think at this point it’s pretty reasonable to assume the worst of email marketers, and I don ’t care if you think otherwise :)