Do you have any personal experience to contribute, or are you just telling us what you contend?
I have had two lap tops and they both had issues, although minor, within the three year period. I'm not even counting this last incident where my daughter spilled tea on the macbook.
It's easy to say you probably won't need it, but with a laptop that you intend to keep for 2 years or longer, the risk is higher that it will have a reliability issue simply due to the fact that it's mobile. Just think about what a laptop is or can be exposed to versus a desktop.
A laptop has a much higher chance of....
being dropped (off your or starbuck's coffee table??)
being hit (travel??)
exposed to varying climates, cold (your home) to hot (nice day where you go to the park and browse the net in the lovely sun??)
getting kicked (your wife kicking your backpack out the way to vacuum??)
getting wet (getting to your car from the park where it started to rain or 3yr old daughter spills tea on the keyboard and thinks it's cool???)
Anyway, I'm sure you can think of your own reasons.