The boot kit come with grease in a plastic package. Only use about 1/2 that.
They have a tendancy to twist at speed, and that can tear them. At the small end, put some axle grease betrween the boot and the axle. And install the clamp slightly loos. That prevents twisting.
The other issue is that the boot can tear due to cintrifugal force. It's just not strenog enough to handle all that weight at high speeds. Fortunatly, there's a pretty simple solution. Simply put a couple of cable ties around the boot.
I was having real trouble with boots tearing. I even managed to tear some heavy duty silicone boots. I got pretty good at installing new boots, as they only lasted a few track days. What a mess. After discovering these simple changes, I'v been using the same boots for the last two years or so.