That's 3 expansions in a row with no level increase. I haven't played those other expansions before, so don't really know what to expect. I've heard for DoN 8 weeks is fine, as you'll mostly still do OoW stuff, just a few extra raids that won't even take a whole raid night. What's the group content like in DoN / DoDH / PoR? Are there things there that a raider would still be interested in? Are there super long and involved questlines (like BiC) in any of them? Are there huge gear replacements that 8 weeks might not be enough to gear out a raid force? Given how GoD has gone, I'm guessing it's fine. People interested in doing BiC are getting them done, people have had time to get their GoD AAs, etc. But being completely ignorant of those expansions, thought I'd get some opinions!
i think 2 months each is ok, DoN is basically a one raid expansion with no AA's to get other then the progression ones. DoDH has some nice fun raids and AA's to grind but then PoR again has limited, easy to do raids with no AA's to earn and little in the way of gear progression. 9 months of being level 70 will feel like a long long time.
8 weeks is plenty for all 3 of them, yes. If it were 12 weeks you'd be gouging out your eyes by the end of the year of level 70.
I don't remember the exact amount of time, but on Fippy, whatever the unlocks were, happened to be waaaaaaay too long. 8 weeks is fine for those, considering there are no levels in any of them and few AAs (or no AAs, I can't exactly remember if AAs were reclassified to Depths or if depths had a few.) Good grouping expansions, some very good raids, but with the current state of the game, how people eat content faster and faster, 8 is enough to fill our hearts with love. . . .