How long should or could you expect them to last before breaking? I am sure that it will vary depending on the bow and set-up. I ask as I had to replace a newer string leach on the top of my string after about 100 shots two weeks ago, and two days ago I had the lower string leach go. Thanks.

That sounds about right.

Get a Meanv2 CSS and do away with the leeches altogether

It depends on what kind you have. The original string leeches (top pic) are "S" shaped and will last no more than a couple hundred shots. The super string leeches (bottom pick) are an improved design that will last thousands of shots.

The super string leaches are the ones that I am talking about only lasting the 100 or so shots and then having a hunk fall off.
I am shooting a Hoyt Magnatech, so an older bow. Am I sensible in assuming that bows, with a higher level of shock/vibration at the shot, are more likely to go through string leaches quicker?

Yesterday I had the top leach that I originally replaced about 80 shots ago, go. Does this mean anything of concern? Or could it just be that my bow has quite a bit of shock at the shot and just will go through them.

I quit fighting all that and went back to whiskers cut down to the size of a half dollar, or smaller... Won't use anything else again!

What do you guys think about the T.R.U. Spyder Speed Silencers ?I am looking for somthing that you can do yourself without a bow press.I had some rubber string tied on before and it fell off.

You can do catwhiskers yourself, without a bow press. And they will last as long as your string does if you do 'em like I tell you.

Take a strip out of the package. Cut it crosswise into two equal halves with a pair of scissors. Place one half on each side of the string and clamp 'em in place with a pair of hemostats. Then take serving thread and tightly tie them into place, with the thread about centered in the rubber. Make an overhand knot on top, then one underneath, then back on top... about 3-4 knots per side. Then finish off with a square knot and melt the tag ends of the serving thread with a match so it won't come undone.

Then repeat on the other end of the string. Then seperate the legs.

If you need more silencing than one strip on each end, you can cut two strips for each end and tie on 4 sections at a time. When you seperate the legs, there will be so many legs that they'll puff out into perfect little balls. Kinda neat looking, but that makes 'em a little heavier and takes a couple of fps off your arrow speed.

I use cat whiskers, put them on an forget them.

I switched from cat whiskers to super string leeches a couple of weeks ago. I had the same results, about 100 shots later I noticed that the top one was destroyed. I have a STS on the bow and will see how it does noise wise when I get it back from the shop with 60lb limbs rather than the 70s that were on it. I know I won't be using leeches again. Cat whiskers or nothing.