You stated in a recent reply that it takes you sometimes 90 days to read an entire manuscript. If you send a manuscript to a top editor in one of the major houses in New York, about how long does it take? I know an agent has no control of this, but ballpark. My agent recently sent my novel out, but I did not ask him how long he thought it would take. I guess I didn't want to seem anxious.
Sometimes overnight, sometimes a weekend, sometimes a month, sometimes a year.
There's absolutely no standard whatsoever.
Generally if I'm doing a big push on a book I think will sell fast and well, I try to get someone to buy it on an exclusive, or preempt over a weekend or a week. Generally however, novels get read within a month or so if you're doing a big push.
Things I'm just sending out cause I've already done the big push and the damn thing didn't sell, those can take longer.
I pretty much pull a submissiion if I haven't heard from someone in 120 days. Sometimes we go back and forth with "I'll get to it soon" and "have you gotten to it" for another couple months.
I've also had editors send rejection letters, then actually read the ms a year later, and reject it again.
Try not to worry about this if you can help it. There's no way to control it, and there's no measure of "what's standard".