Now that Elysium has all vanilla content pretty much scripted consider releasing content at a more blizzlike pace in terms of progression.
In retail vanilla content took much longer to clear for various reasons. Players didn't understand the game as well as we do, for the most part didn't optimize gear or raid comp as much as is done on private servers. Worse (or no) addons, on top of all that many final raid bosses were very buggy causing guilds to give up attempting them until they were changed. All these factors served as a gating mechanism, keeping the carrot on the stick dangling in front of players in the form of unkilled bosses to progress on, race to world / region / realm first on. Those things really don't (and can't) exist on a private server 12+ years after the fact.
We on private servers have content on farm for far far too long in-between raid instances, our raids have significantly more of the later boss gear when moving onto the next raid then any retail wow guild had.
Here are some numbers from retail compared to the Elysium servers.
Ragnaros killed April 25th 2005
BWL released July 12th 2005 - 78 days later
Nef killed Sept 26th 2005
AQ War effort Jan 3rd 2006 - 99 days later
C'thun killed April 25th 2006
Naxx released June 20th 2006 - 56 days later
Ragnaros killed Jan 18th 2017
BWL released July 12th 2017 - 175 days later
Nef killed July 12th 2017 - Currently 50 days out
Don't have data from realmplayers for MC / BWL
C'thun killed April 26th 2017 - Currently 127 days out
The way the releases are coming on the Elysium project now, players have easily twice the amount of loot from the later bosses of the instance then any guild had in vanilla wow, seeing that the end boss has a drastically higher ilevel then anything else in the raid this makes a huge difference.
I suggest that you take the retail time between the instance being completed and the next one being released into consideration as well for the release dates of new content. I think that having less of your raid with full BIS going into the next tier of content will make that content more difficult and will lower the burnout players experience when farming old content for long periods of time.