One of the things I like the most is, yes the designers can't really work until they can be in the theatre, but it gives you such a rush of enthusiasm to get all of the costumes, set, and goodies at once, and then off you go with all of the imaginary things made real. Having the tactile experience of the technical elements in concert launches you into the run with great energy... It's by necessity that tech comes last, but emotionally it feels by design; after all the austerity and privation of rehearsal, you are rewarded with a surfeit of technical riches just before you do it for a paying audience.
Of course, this is also a scary ass time because you've got to make all the technical stuff work and everything is new and the audience is paying to see you in TWO DAYS. In my experience it takes a full day to get through Act I and then another day to get through Act II, on the third day you get a dress rehearsal in the afternoon and then your first preview that night.
Somehow I'm always in shows with a hundred ensemble characters and the tech can be a nightmare changing in and out of every costume in time for the next scene, but we've been pretty fortunate so far with this one. There's one big hairy moment we'll have to look at during the dress, but I'm sure it'll work out. It's all about teamwork and we have a really great team.