I believe the magenta stripes plagued the JVCs with the older chassis (RS15/25/35) and older, but haven't seen any reports since.
JVC came out with new lamps with cooling flaps to the 2011 models, but as far as I recall they still burned out fast. The 2012 lamps though seems to be really good over the board. I haven't heard anything about any pre-mature bulb failures and they even seem to keep their brightness more than one would expect compared to other projectors. Many have reported 3-400 h and still 100% brightness, this many hours would otherwise typically show 15-30% drop in a bulb based projector.
I believe the problem of the older JVCs were a design flaw that prevented proper cooling of the lamps, which subsequently overheated. The RS46 has a completely redesigned lamp and lamp housing to allow better cooling.