how much psi is braided steel line rated for?

a little history. a year ago or so i bought a used nitrous kit off corral for $225. turns out the bottle leaked badly. so after dumping 15lbs of nitrous into the atmosphere i bought another used bottle off ebay for $100. not quite sure why i thought someone would sell a working bottle off their nitrous kit, but i did. it leaked out too. so about 2 weeks ago i bought a NEW bottle and gauge and got it filled (3rd time). everything worked fine for a week or so. so friday after work i decided to open up the bottle and see what kinda pressure it was making after sitting in my trunk in the sun all day in 90+ heat. it quickly pegged the gauge (1500psi). i get a few hundred yards down the road and all of a sudden i hear a loud band and hear gas dumping out under the car, like a LOT of gas. i immediatly pull over and as im going to the trunk to close the bottle i can feel the cold gas pouring out by my feet. i shut off the bottle before it all leaks out. i did a quick visual of the line under the car and didnt see anything but i know thats where it broke. so now im out another $50 for a new line and $50 to get it filled AGAIN.

so, for my questions:
i figured the braided steel line would be rated for at least as much as the bottle (it says 3000psi), apparently i was wrong. is the line old or was i just stupid?

also, do you other guys with n2o leave your bottle in the car all the time (in the heat) or just put it in when you plan to use it?

thanks.

i havent pulled the line out yet to inspect it closely, but it is running through the trunk floor and also close to the exhaust at one point. and i know its not the safety valve because it was dumping under the car and i dont have a blowdown tube. i guess well see where the problem lies when i yank it out tomorrow.