You should take your Mac to the store and have them take a look. Or at least run hardware diagnostics. I've been using Macs for well over a decade and in that time I have maybe seen 4-5 crashes total, across multiple laptops and desktops. A crash every two weeks is not a normal situation in OS X.
Just yesterday, OSX was convinced that I had an external monitor. I did, but that was 2 hours back when I was at the office. So I got to the preferences screen and.. the kernel crashed.
Do you have some kind of third-party display or window manager installed? I regularly (as in "every day") have my Macbook hooked up to dual monitors and I've never had the kernel crash due to a disconnect or a change on the preferences screen. Does that happen regularly for you or was that just a one-off occurrence?
I've got an otherwise unexceptional LG monitor that with one specific generation of MacBook causes all sorts of problems. My windows machines and newer macbooks don't have this problem, and connect to the monitor fine.
