We still make sure one or the other is set, but it really doesn't take that long. I can't remember very many times that's why I delayed stepping away from the ball. Maybe a couple times per game at most. You wouldn't blow the RFP until one or the other was set previously so this is not much different. If they are delayed enough causing the play clock to run below 20 (or enough to put the offense at a disadvantage to be able to snap the ball) you can always reset it to 25 and try again. Most of the time one of them is there and ready to go within a couple seconds of the umpire placing the ball.
With all do respect Brian, we have some "issues" to resolve with some chain crews intentionally holding up the game, thus, "We" will NOT be waiting to
"...make sure one of the other is set..."Don't get me wrong, there will be some common sense inserted here (eg; 90 yard pass play, ect.) However, the days of the chain crew crawling to their position as (unofficially) instructed by the Home Head Coach officially ended with the insertion of the 40 second clock! In the extremely unlikely event they are not set when the snap is imminent, the H simply drops his bean bag, and the chain crew sets up on the bean bag.
As one example, for the last several years, under the 25 second clock, my crews have been informing the chain crew this is the mechanic. While many may consider it a miracle, but the chains crews gain some superhuman speed, AND the most important part, in 4 years time, my H, has yet to drop his bean bag for them, NOT EVEN ONCE!
You gotta work with them, you gotta be professional, you gotta respect them, but they gotta put out a little effort now and then.