YLOD symptoms. which mean overheat issue. its depends your ventilations ,what games you play and how many hours gameplay;very sure mostly phat unit user never really maintain like change thermal paste per year once. but your case already reached the YLOD stage so have to repair.

the only games can get overheat easily for phat unit.

- Modern Warfare 3
- Battlefield 3
- Uncharted 3 (you can actually read their forum)

any other games sensitive im not sure.

etc; any games start from firmware 3.70 to 4.0 problem it comes very common overheat for phat unit because the mobo gpu cannot reach the requirement for new games and i estimate after repair the console if keep playing new games most can tahan 2-3 month its consider very lucky ,yes,can repair but try the best remain go back to old games . 

so its depends on your decision;some people wants to repair just to backup their data and shift to slim unit.this is what i can see my experience, so correct me if im wrong

seriously YLOD repair are useless , back up all data while the console can last at least 30 mins .. go buy brand new PS3 slim , transfer all old data to new PS3 slim

the CPU between phat and slim are totally different , the latest ps3 slim model are 3000 series which use 45nm cell - 40nm rsx which run 200 watt max .. here are some guide regarding ps3 slim models

CECH-2000 ** 45nm cell / 65nm rsx - 250 watt max
CECH-2100 ** 45nm cell / 40nm rsx - 250 watt max
CECH-2500 ** 45nm cell / 40nm rsx - 250 watt max
CECH-3000 ** 45nm cell / 40nm rsx - 200 watt max

the most important here is , console always get good air ventilation .. ps3 phat may be need once a year maintainance , ps3 slim i dont think so cause the percentage of YLOD considered as " rare  ".. the hardware also much more reliable plus less heat