I replaced the bulb twice in my Samsung. The original bulb lasted just under 3 years. Bought a third party bulb which lasted a year (around $100). Then another after a year for $70. Sold the TV and went with a plasma. I would recommend sticking with OEM bulbs after my experience. As mentioned above it's easier than expected, especially if you replace the housing.
/sidenote I really wish they made a panel that was 50-51" instead of 47" or 55" or I may have gone with an LED backlit TV. However, I've had my plasma a week or so and couldn't be more pleased. It'll take me a month to try out all the features (SmartTV, DLNA, USB multimedia support). I also bought from Amazon and received a $30 credit as the price dropped since my purchase. I was able to get $300 cash locally for the old TV (4.5 yr old Samsung 720p Slim DLP)