User blog comment:B214/Question and Answers 6/@comment-3285616-20161121005601/@comment-10330822-20161123082328

I'm afraid I don't really understand the confusion. The seasons are covering about 2 light novels per season. So every LN is about 6 episodes. In shonen manga, excluding the usual filler, anime episodes cover about 2 to 2.5 chapters of manga. Meaning that your average season would be about 12 to 18 chapters in manga-terms. They do seem to be rushing the series a bit, as we've already seen some stuff from Volumes 9 and 10. My guess is that they want to make sure they end next season on Volume 10, with Issei vs. Sairaorg. Because if you end on Volume 11, you get a cliff-hanger. Volume 11 needs to be in the middle of a season, meaning its better to do it after Season 4, in a hypothetical Season 5. This series isn't going to be that big. The light novels have a lot of exposition in them that the manga and anime don't need. Things like physical descriptions, facial cues. All of those can just be shown. Also, Azazel and Issei don't do the same amount of "mental talking" that they do in the LNs. So there is a lot of script to remove. So far, excluding the crap the pulled at the end of Season 3, they've been doing a pretty good job covering what they need to cover. There are 22 volumes right now, so, given they cover 2 volumes a season, that's about 11 seasons worth of material roughly, excluding the three they've already done. Which would be about another 96 episodes, or 192 to 240 manga chapters worth of material left to catch up to the LNs are now. That's not a huge amount of chapters all things considered, but it'd still be a pretty decent sized series.