You've got a heavy and sharp metal object spinning around at 3000-3500rpm. Your floorpan, (assuming it isn't typically rotton, like most are), is only what, 2mm thick?
Over the weekend I gave mine a proper valet for the first time since mine failed a few weeks ago, and when I removed the drivers rubber mat, (no carpets), the damage done to the floorpan when the prop snapped at just 20mph was quite alarming.
The torque is split 50/50. If the front has snapped / failed, then the rear aint going to be far behind it. A thought that was confirmed when I removed my old rear prop, re-filled it with grease, and the UJ's were still stiff.
The total price inc VAT for new front & rear props from my local LR main dealer was £460, so for the sake of argument lets say that a rear prop is £230. If anyone on here thinks that their life is worth less than a couple of days wages, then by all means leave your proberly already knackered old prop on untill that fails as well.
Just don't forget the consiquences of it failing at 70-80mph and ripping through the floorpan and the vehicles occupants like a hot knife through butter.
Personally I consider my life, or at the very least the cost of replacing the floorpan, (again), to be worth more than the price of a couple of brand new props and assiciated nuts & bolts.