The last time I did 400 repeats it was after a 14 mile long run. I knocked off six (of 12) laps in under 1:45. Yesterday, after 20 miles on Sunday I was feeling fine but not very sharp. Very lethargic and spent. None of the dozen 400s came in under 1:45.
And I didn't care. It felt fine. I maintained 1:45-1:55 times for the most part and never felt not up to the challenge.
Best of luck to everyone running Chicago this weekend. The big triple of marathons is upon us and there's a whole lot of tapering or peaking going on. I still have a 15 and 20 to do before New York. I really just want the "cool" low 70s to come back this weekend.