I'm thinking about upgrading my lighting, and see an array of different warranty options, which directly correlates to price. What is the "normal" life time or failure rate of these lights or ballasts. Thanks.

Ballast are solid state and should last indefinitely. HID bulbs dim over time, but typically have an expected lifespan of 2000+ hours.

so I shouldn't assume that deals without lifetime warranties are of lower quality than those with the lt warranty

That's not exactly a safe assumption. Lower end bulbs have less heatsink material connected to the electrodes, so they burn away faster. Lower quality components in cheaper ballasts have a higher chance to fail too. What I was listing in the previous post was best case scenarios. Technically there are no "wear" parts inside of an HID ballast, so as long as the components are up to par and the solder joints are all perfect, they could last for ever. HID bulbs all dim as they age, how quickly that happends depends on the qualtity of their design and construction.

so as a sound minded consumer, one should probably go with the life time warranty option

If you plan to have the kit on your car (and own the car) for several years, then going for a kit with a lifetime warranty is certainly a good option.

This might help you further in your decision:
http://forums.bimmerforums.com/forum/showthread.php?t=356013&highlight=xtec

Steve.