The design process is becoming a little more streamlined, too - at least as far as houses go. The basic structure for a lot of scenes will reappear from year to year, just with new scenic on top of it. The warehouse staircase in Purge was identical to two Walking Dead houses. The subway car in Dead Exposure was identical to Deadtropolis. The design of the slanted floor in Seeds was identical to Forsaken, complete with scare locations (you just walked the opposite direction). There's also the potential of the Sprung Tents or MIB to just get new scenic/paint and creatures for a "new" house with the exact same layout (like the Spawning into Havoc; they didn't even strike that house).
That definitely saves time on the most time-extensive part of house design. It ALSO complicates the actual house production, because it requires coordination in ensuring that key props/scenic pieces are available. If multiple houses have similar design needs, this is even more important.
Time is ungodly short on getting stuff ready for this year. Starting 6 September means everything has to be "show ready" two weeks earlier than last year, and last year they barely finished in time. The extra production assistance is critical in helping smooth that sort of stuff out.