Wednesday. Wednesday is typically the "Oh crap i have a wedding this weekend and I need a harness for the weekend, can you make this work" day. I probably get 2 or 3 emails a week to this effect.
I really dont mind because... I LOVE a challenge, if you take a look at a harness you like and you're needing a super quick turnaround, just drop me a line I can be pretty accommodating.
Just make sure you get the request in early enough, up to around midday is the sweet spot.
Oh and leaving me a tip is always super nice if I am rushing you through a harness. Don't be that guy.