A lot of people have talked about liberating and backing up their content. Another approach is to recognise what you are actually paying for - a kind of extended rental - and adjust what you are willing to pay for it accordingly.
In my own case, I have never bothered deDRMing any of my Kindle books, even though I vaguely thought I might. They simply never go to my PC. I enjoy the convenience of being able to buy things and have them turn up automatically on my Kindle. I'm not in a great rush to give myself a lot of extra work obtaining and organising the backups.
I might live to regret it, but I have no complaints so far. If I didn't build up so many unread books, I'd probably never care. I'm not a big rereader.