The YLoD is a general hardware failure that is typically either fatal MoBo damage due to thermal cycling through repeated use (solder joint failure) or PSU failure (power supplies do die as well). If it's the latter, you have an easy and permanent fix. If it's the former, you get a temporary fix at best.
I've been through three YLoDs on three separate consoles, so I am familiar with the repair process.
The heat gun reflow repair does work, but it is and should be treated as a temporary fix. If you can successfully repair a PS3 this way, IMMEDIATELY copy and back up your data and treat anything on the repaired PS3 as disposable information.
I've had repairs last anywhere from a couple months to a couple weeks to a couple days to give you an idea of how unreliable repaired consoles can be.
Using higher quality TIM (thermal interface material) won't magically ward off future harware failures as even the best ones are only good for single digit temp drops. What they will do is provide the same level of thermal tranferance (or slightly better) as when the console rolled off the assembly lines. Over time, the stock TIM SCE used dries out, losing its effectiveness, leading to overheating.
