When swapping leads (and considering how crucial the JN is) some leaders may also not like clipping a JN that they did not place themselves but, again, you could say the same of the entire belay.

In all these situations, the leader can always pick another pro from his/her replenished rack to double-up or replace a less-than-perfect Jesus nut or swap a pro that might be needed to protect the next pitch.

From a Fall Factor viewpoint, this makes sense. From a speed viewpoint, it would slow the team down.
Just make sure you & your partner both know what's going on.

The next lead would go ...

a) climb up to the preplaced JN and draw;
b) clip it;
c) lead on.

One can still get a FF2 during 'a' and, if clip is blown, during 'b'.

The main benefit here being if the placement is difficult meaning pre-placement makes the difference between the leader of the next pitch clipping just in time versus falling while placing pro. I can't think of cases where preplacement seemed warranted but then maybe that's because I have not given this a lot of thought - not sure.

With modern belay devices, gloves, and a decent and well-arranged belay anchor, I have not been overly concerned about a fall factor 2. There may be special cases but it doesn't seem to me something that would become a normal practice (but maybe in the "bag of tricks").

Bill L

There is no reason to place a "less than perfect" piece of pro. If you are going to place it, it had better be bomber. If it won't be, make the leader make their own choice (with a full rack to use).
...

Not quite true. There was a good discussion on the subject not that long ago.

Unlike previously believed rope does recover much quicker after gear pulls. In other words, you will slow down and hit your next piece with lesser force.

And you are more likely to be oriented properly as well. Bottom line (IMHO) marginal gear is better than no gear.

There are a couple of zipper videos from Indian Creek to support this. A number of cams pull out, guy decks but walks away

Ah, but there is redundancy in the belay.
....
There is no reason to place a "less than perfect" piece of pro. If you are going to place it, it had better be bomber. If it won't be, make the leader make their own choice (with a full rack to use).

I was under the impression that a "zipper" was when the gear rips from the bottom up, due to the lack of an upward pull piece, and hence only the top piece ever sees weight.

Whenever I have done this, I've clipped the rope into the nut, and then downclimbed back to the belay. This way it is pre-clipped for the next pitch, and there is no chance for a factor 2. This cannot be done if the pitch is a true rope stretcher, but I find it is very uncommon for me to use all 200 feet of rope in a pitch. I have used this trick in situations where the climbing is hard right off of the belay, and a fall before getting in pro would be nasty.

If the JN is placed by the leader of the previous pitch, the placement could be done in the safest part of the pitch: at the end, with the most rope and pros to protect a potential fall, and just above the belay stance where

On a blocky climb, placing the JN at the end of the pitch means that the fall length will be at a maximum, because of slack and rope stretch. This maximises the chance of hitting a ledge, resulting in a broken ankle or worse.

Did you really mean to use the word "maximum"?

The maximum fall potential is generally found at the early parts of the route, unless you didn't place any protection at all, in which case never mind, Dan.

As for 'slack and rope stretch' - what? Once a higher protection piece is placed, regardless of whether the first climber is downclimbing or the second is starting on the next pitch, they are on top rope.

In fact, re-reading your post I can't make any sense from it at all!

Just be sure to always belay in a way that if the out-of-sight second falls, the JN piece blows, you are ready to handle the ~180 degree change in direction of pull. I know - the JN is supposed to hold a leader fall.

It's a crap shoot whether the belayer will react quickly enough with a tube-style belay device if the JN fails, whether by fall of a second or by fall of a leader. With a leader fall, at least it's likely you will literally see the fall unfold.

Ah, you may have misunderstood my methods. I climb up and place the jesus nut, clip it, downclimb, but then belay off of the anchor with an autoblocking device. I rarely belay a second off of the harness. The jesus nut is not used in the belay of the second, but is pre-clipped for the start of the next pitch.

Then it seems like this would be a pain in the butt if swapping leads. But maybe not so much of a pain if only one person is leading ... assuming one can easily grab the strand going from the JN directly down to the second.

You just have to pull the rope through the JN when swapping to get to the new leader.

... essentially restacking the rope each time if swapping leads.

It's not a big deal. Efficiency is important to me for the climbing I like to do. But I should say in the same breath, I was once bitten pretty hard in the name of trying to be efficient.

Cheers!
Bill L