1 Year.

There are many people who make event specific emails addresses. These events are annual, so they use the email yearly.

1 year is still far too short (and only a touch longer than the current 270 days). 5 years is more reasonable. It costs them so very little to keep the data, and it costs people so dearly to lose emotionally important stuff over a technicality.

That's not what I meant.

Email should be kept forever. I meant if you don't log in for a year they can delete the account.

I disagree. I can see them freezing the account - i.e. rejecting further mail to it. But if I come back after a year, I fully expect to be able to say "hey guys, I'm back, can I have my emails now?" and get at it.

Data storage is ludicrously cheap that I don't understand why there's a need at all.

Data storage is ludicrously cheap unless you cater to more people than most countries have. Years of email times 10s or 100s of millions of people probably isn't that cheap.

Drop Box reserves the right to delete free accounts after just 90 days. Is that unreasonable? Hell no. I bet they don't hold your stuff forever in case you do pay that overdue bill one day too.

I'd make it two years since sometimes things are off by a week or two.

Additionally, they should not delete any existing mail, but instead move all new mail at that point to spam, which I think gets deleted in one month.

This way you never lose anything you actually know about. And you have recent email just sent to you. The cost of this should be very low.