I have all the Heyer's, now, thanks to two different year's worth of sale prices. Like you, I spread them out. Saving them for when I'm feeling like a bit of a fun break.
Well, that's no way to behave. Bad Charlie!
But seriously - if you have lots of ebooks to read, there's no point in buying more at full price unless you're going to read them instantly (i.e. new release of the next book in a favourite series).
I know, I know. Bad Charlie! But I was feeling down and let it get the better of me. But at least they were books in a series I knew I really wanted to re-read. And that I had NOT been able to get from the library. (Others in the series, I had gotten from the library.) And they were $8, not the $13 they had been when I last looked. But still, no real excuse.