IMO, TLC NAND is a non-issue from a practical, everyday "consumer use" perspective. The 840 EVO is a "consumer" drive and if your usage follows that assumption then your drive will last longer, much longer than you would ever use it for. Enterprise environments are a different issue.
Think about this practically.
If you buy a Samsung 840 EVO 120 GB today, how long do you honestly think you will use it before you run out of space (120 GB is considered pretty much "entry level" even today) and buy another newer, faster, larger drive?
How much data do you think you will write on average to your SSD every day?
Lets assume its 50 GB PER DAY, which is HUGE BTW.
Even with 50 GB of writes EVERY DAY, your 840 EVO 120 GB has a life expectancy of .... wait for it almost 8 YEARS!
Do you honestly believe you will still be using a 120GB SATA 3 SSD 8 YEARS from the day you buy it? Don't forget, a life expectancy of 8 YEARS is based on the fact that you write 50 GB of data EVERY DAY.
Somehow I doubt you will hit this sort of data transfer every day from a consumer standpoint.
If you buy a 840 EVO 250GB (and this is -THE drive- I recommend to people), and write 50 GB of data EVERY DAY, your drive has a life expectancy of almost 16 YEARS!
There's no question that MLC NAND lasts longer - much longer but its a question of practical, common sense. Whats the point if your 128GB MLC drive lasts 35 years? Do you see yourself using it at the point? Will it even be supported by the hardware at the time?
Stop worrying about TLC NAND - its perfectly fine for consumer use.
And FYI, I got the figures I posted above from the below article in case you want to read it more thoroughly -
http://www.anandtech.com/show/7173/...w-120gb-250gb-500gb-750gb-1tb-models-tested/3
Here is the conclusion from the above article in case your're a "TL;DR" person with the important parts in
BOLD &
UNDERLINE for easier reading-
Using the 1129 cycle estimate (which is an improvement compared to last year's 840 sample), I put together the table below to put any fears of endurance to rest. I even upped the total NAND writes per day to 50 GiB just to be a bit more aggressive than the typically quoted 10 - 30 GiB for consumer workloads.
Endurance scales linearly with NAND capacity, and the worst case scenario at 50 GiB of writes per day is just under 8 years of constant write endurance. Keep in mind that this is assuming a write amplification of 1, if you're doing 50 GiB of 4KB random writes you'll blow through this a lot sooner. For a client system however you're probably looking at something much lower than 50 GiB per day of total writes to NAND, random IO included.
I also threw in a line of lifespan estimates at 100 GiB of writes per day. It's only in this configuration that we see the 120GB drive drop below 4 years of endurance, again based on a conservative p/e estimate. Even with 100 GiB of NAND writes per day, once you get beyond the 250GB EVO we're back into absolutely ridiculous endurance estimates.
Keep in mind that all of this is based on 1129 p/e cycles, which is likely less than half of what the practical p/e cycle limit on Samsung's 19nm TLC NAND. Go ahead and double those numbers and then you're probably looking at reality. Endurance isn't a concern for client systems using the 840 EVO.
