If your 2-3 year old Mac is running very hot and slows down after a minute of heavy use, clean out the dust from the cooling system instead of buying a new
How To Clean A Laptop Fan (Step-by-Step Guide)
How to clean your MacBooks fan and prevent overheating! - iFixit Repair Guide
How to clean your MacBooks fan and prevent overheating! - iFixit Repair Guide
How to clean dust from fans on Apple macbook pro inside - YouTube