I used to really worry about this sort of thing, and would only buy ebooks from vendors like O'Reilly or Baen because they were DRM-free, and I could read them

I used to really worry about this sort of thing, and would only buy ebooks from vendors like O'Reilly or Baen because they were DRM-free, and I could read them forever. These days, I can't be arsed to worry about any of that. I just buy what I want from where-ever (Google, Amazon, etc.). Why? Convenience of course. Really, how many of these books am I ever going to read again? Tech books in the old days (1990's) would last you a few years at least (my copy of TCP/IP networking from O'Reilly was well-used) but these days? Everything is changing so fast. So I just buy them, enjoy them, and don't worry about having access to them in the future. A few true classics I have purchased multiple hard copies of over the years anyway. If I end up purchasing electronic something for a 2nd time, I might make more effort to ensure continued access.