oh I completely agree its better to have the right amount. but with 360s its better to err on the side of caution; I've fixed well over 100 xbox 360s.
I hope you aren't doing it for a living, or at least have good tools for getting that %$&*& case apart. As luck would have it, and probably as a direct result of me posting in this thread, my son-in-law's 3-year old unit RROD'd on him. Being the family "electronics fixit guy" I ended up with the job. It was time consuming, as I didn't have the proper tools and hardware on hand and had to find my security bit set in the middle of the teardown, as it was the only set to have a T8 in it. The case slowed me down big time.
To anyone considering fixing your own, it's not that bad. If you can fix an overheating PC, you can fix an RROD'd 360. Here's some notes that will hopefully save some folks some of the problems I ran into;
1: Get the kit. The real one with the unlock tool. You can get by without it, but your case will never be the same unless you have 4 small flatheads and an extra set of hands.
2: Watch
this video a few times.
3: Use the right hardware. If you have the real kit, then you should have it already. I didn't and needed to modify the fins on the big heatsink to accommodate the extra length of the screws I had on hand (joystick mounting kit screws fit the threads on the heatsinks.

) I also needed to drill out the only nylon washers I had that were close to the correct size.
4: BE CAREFUL PRYING OFF THE X-CLAMPS!!! If you slip and gouge the board, U R SCREWED! Take your time!
5: Make sure the top surface of the chip and the associated area on the heatsink are
spotless. The paste used by MS gets to be the consistency of baked on chewing gum, and it's hard to get off. If the kit you buy comes with cleaner that works well, so much the better. But I ended up using brake cleaner, after alcohol, contact cleaner and acetone failed to cut it.
6: Don't even think about starting the job without that T8 bit. Big Lots sells a security bit set for $3. Get one.
7: Take your time and make sure you have plenty of room to work. I don't usually work on these types of things and had XBOX 360 all over the place

.
8: Make sure you remember to plug in the DVD unit at the testing phase. I think they left that out of the video and it fooled me into thinking that the repair had failed.
9: Don't even think about re-using the "X-clamp" thing. You went through all the work of getting to the board, just fix it properly while you are there.
When I was done, I played a CODWAW demo for about a half hour and it was pumping some serious heat and never glitched, nor do I think it ever will again. All in all, it's not difficult if you have the right materials and it's better than buying a new one or waiting a month for a unit that will probably just do it again.