That's true. It is a bit harder to find parts for laptops. I probably wouldn't be able to swap the old parts with the new parts myself either... Not a big deal though I know some people who prolly could do that.
yes upgrading a laptop is the most boring job in the world if you have to change the GPU or CPU (its a complete strip down of the laptop just to get at any of them) the ram and hard drive/drives are easy enough to get to tho.
laptops were never really designed to be upgraded alot and for that reason you end up having to do alot of work just to get at bits because the laptop needs loads of case surface to make it strong enough to deal with it being moved around and knocked etc.
to be fair i do own a laptop (Panasonic Toughbook) but i only ever use that for working on car ECU's and car electrics just for the fact that the battery life when trying to game on a laptop is very poor when your stressing the GPU, CPU and RAM all at the same time.
Also mGPU's tend not to stay in date for more than a year and there for if you want to play the new games every year you need to look at buying a new laptop. You might find the mGPU will last two years depending on what games you play tho and how many FPS you want from it but when you compare the mGPU to a desktop GPu which can last 3 or 4 years plus its easy to see why people say buy a desktop over a gaming laptop.
also another issue you will have if you want to buy a gaming laptop now is the fact that AMD have very good mGPU's out at the moment (ive seen loads of people go for and tell people to go for AMD mGPU's over Nvidia) (so it would seem that AMD has found something its good at at last lol) but this leave you with the issue of you want an i series CPU but you also want the AMD mGPU so which one do you give in on. The only way that i can see you being able to get round this at the moment would be to wait and see what Nvidia's new mGPU's are like in Q2 of 2013