How Many Staples Per Flip?

I like to put in three with a flat cinch stapler; the first staple is on the opposite side from the fold, and the other two form an equilateral triangle close enough to the coin to ensure it cannot squeak between two staples.

Honestly, as long as it's tight and the coin won't slide around, it doesn't matter. If I had 1200 to do, I might try to do 3 per flip which will save a box of staples and 1200 squeezes of the stapler.

The folded edge doesn't need a staple because its connected, so only 3 staple's are needed but I use different flips then Shale`s. Mine are smaller and I like them because they save room. Which coins do you have 1200 of to encapsulate?

I staple mine as shown in the example photograph, but I am very picky about my coins moving around at all, so I like stapling them on all four sides to "lock" the coin in the center as much as I can. Just one of those things I do differently from most people.

I always use 4 it makes it tighter.

I use four. I like the symmetry. I usually write the info on the upper corner so having 4 staples doesn't interfere with my labelling. Most of my coins are in albums or airtites, so I don't worry too much about how many staples I am going to go through or how tired my hands may be... but if I was doing a very large quantity like you are, I might re-think the process.

I use 3 staples (flat cinch) unless the coins are really thin and small like 3 cent silvers, won Barber dimes, etc. then I use 4 staples.

Just remember that if you plan on ever opening one of those, might be in your best interest to move the staples a bit farther from the coin.
I always remember what happened to me. I purchased a 1921S Lincoln Cent in MS-64 and it was in a one of those flips. I used a screw driver to pry open the staple and it slid across the face of Lincoln. True, shouldn't have used a screw driver but to late now.
Just remember that when you put those staples in place.
AND if you have time, use 3M tape instead of staples.