To the question "are the files on OneDrive saved forever?", OneDrive's team answered "You'll still be able to view, share, and download files, but you won't be able to upload files until you buy more storage."
This means that you can upload as many files as you want over the course of a year, allow your subscription to lapse and still access them later without limits.
Google also allows you to do that on Google Drive although if you're over the free storage limit, incoming messages to your Gmail account will be returned to the sender.
Will Box and Dropbox follow?
Microsoft removed the 1TB storage limit on all Office 365 subscriptions, although the rollout has been staggered and likely to reach non-business users early next year.
A 10GB limit on individual files and a 20,000-file limit for OneDrive for Business still hold although you will be able to upload as many files as you want if you compress them.
The cheapest way to get unlimited OneDrive storage is to get a one-year subscription to Microsoft's Office 365 Personal which costs less than £50 at CCL.