Personally, when I do my first series, I'm planning to get the whole series up at once. We'll see how that works for me, I guess. My thinking is that consumers are being trained to prefer binging thanks to Netflix, etc. Even having the others available for preorders won't satisfy those readers who just want to read the whole series through at once. So, since that's what I'd prefer as a reader, that's what I'm planning to try with my own books. But like I said, we'll see how it goes. If it's a total failure, I'll probably try something different with the next series.
Actually, now that I think of it, there's a trilogy I may put out before that series that I'll likely do each as they're ready, but those ones aren't as closely tied as the other series (more like three related standalones than one continuous story), and they're planned as shorter books, so they're less of a big release. So maybe it also depends on the series. If each book is mostly a standalone, spreading them out is probably more okay than if it's basically one continuous story.