For me it's valid if I use the software a lot. But honestly if the piece of software doesn't gain any new features because you paid for it versus pirating, it's not worth it. Multiplayer games are a good example of software that gives the user a lot of content in exchange for DRM and cost. WinRAR on the other hand doesn't change at all even if you pay for it.
Yes, it should be enough reason to buy software with DRM even if it doesn't give you any benefits versus pirating but nobody does that.
TL;DR I think DRM is good for multiplayer games and software that has official servers for updates, content etc but DRM is not good for software that doesn't benefit from network content, i.e. winrar, cd burning applications
It will ultimately be circumvented and those without the DRM will have a better experience. This is the manner of things that is "give an inch, they take a mile". You can already see this with singleplayer games that require an online connection for no reason.
Regardless, most DRM is proprietary, so I wouldn't use it anyway. I donate to Free Software projects and it's a far better arrangement.