Jesus Christ, I just pressed the submit button and got an alert. Easy there, Tiger.Legit just bought the Samsung 750 EVO 500GB about 20 seconds ago :/
The 850 Evo isn't a bad SSD by any means. New 3D TLC NAND is better than the old TLC NAND, I simply prefer MLC NAND over the other. You can cancel your order or get it. I think the 850 Evo is good for 1,000 TB of data before it goes kaput.
Edit: Just looked it up. It's been tested to beyond 650 TB of data written, cell degradation starts at around 800 TB, and then it goes downhill at a slow rate. To be honest, I really wouldn't worry. It's got a 5 year warranty and Samsung replaces bad stuff without question. You probably won't hit 300 TB of data written before you get a new laptop or a new drive.