Hmmm... I just give some comment..

I notice YLOD is a symptom of few incident

1. The processor / mainboard overheat and causes the solder to detached it self and hence cause malfunction to PS3

Preventive solution
I have a notebook (Compaq V3000) and it suffers very close to the same stuff (get hot and solder melt) how I prevent this... I open up my notebook every year and perform heatsink and fan cleaning and it is now 5 years and my notebook just run cool and like new...

My solution for PS3 (Fat or SLIM) if you dare or after warranty you can actually open up the PS3 unit and clean the heatsink and Fan, years of dust will degrade the performance of cooling and the efficiency of airflow inside the unit and with this result it will get HOT and solder inside will melt... (it is logic....)

If it is under warranty by Sony try send the unit in for a annual dust removal just tell sony my unit get very warm and will like you to service the internal fan. (under warranty most sony will give free service)

like this your internal cooling system will run at tip top condition and this will prevent system overheat leading to YLOD...

2. YLOD is caused by the voltage converter or Inverter...

Solution.
Dirty current by TNB we all know and we all pretend dont know hahaha
our TNB current fluctuate and if you have air conditioning at home you will notice your light flicker once the compressor fire up...

my solution to prevent this I use UPS (yes Power Ups Backup) I hook my PS3 and my HTPC into it... it provide stable current, clean current and during blackout you can shut down your PC and PS3 properly to prevent HDD crash (Data loss)

3. YLOD caused by Bluray drive failure / or Bluray Drive Failure

Solution.
None basically..... replace your bluray lah if it fail...
some suggest not to leave your Bluray in the tray... but I think this is OK

I dont recomend you to watch pirated bluray @ PS3 reason being some cheapo bluray is not balance and cause vibration... this will spoiled your unit... expecially when you notice the bluray disc has a very thick and un even printing.... very bad.

300 + - depend of brand on the Backup UPS go find at LOWYAT plaza lor and bargain hehehe

You can but you need to clean the internal fan and do some basic servicing...

It is like buying 2nd hand car, once you get the car you'll send it for a basic servicing... like wise I suggest to remove the dust from internal fan and heatsink... who knows the play station you get is been sucking in dirt and dust from previous owner...

Downloading will not take alot of processing power... heck My Dell Zino HD has been running 24x7 since the 1st day and it has been running non stop for a YEAR... no issue also...

the problem of YLOD is when you play high processing power hungry games that push the CPU and GPU to the max and run it at a period of time it will cook!!!

it is like running your kancil at 180KMH for 5 hours... I bet the tyre will fall off hahaha if you drive a kancil at 20kmh heck you can drive it for 50 years!!!