Ok, there is also a work round with subscriptions via Amazon UK at least. Go to manage my kindle page, subscription settings, then actions for the periodical you want. Click on download and transfer by usb. Choose transfer to whichever device you want, and save the file anywhere convenient. Add the book to Calibre, usual disinfection routine then THIS IS IMPORTANT edit the metadata to change the title. If you don't then you will have a years worth all with the same title that will show as duplicates that can rather easily get deleted by mistake (Go on, ask me how I know this) Duh!
Voila! Saved for ever!