The only question is how these drives fail when they reach their write cycle limit, do they just stop writing? Start writing crap?
The conception that drives just become read only is mostly untrue. Generally speaking, what happens is one day the drive gets powered down and it never starts again.
In certain circumstances, I have seen SSDs become read only, but their retention period is usually only a day or two by then.
Here is the good news: You're never going to wear out the NAND. It's just... impractical. Especially with larger capacity drives.
For instance, here is my Samsung 830 64GB:
See the last SMART attribute? Multiply that number by 512 to get bytes written. In this shot, that's 412,025GiB, or 402TiB in this picture. The drive has been writing as fast as it can for the past two months.
See the attribute 177 "wear leveling count"? That's the average number of PE cycles expended. Each time a block gets erased, and later written on, that count increases. The 830 uses 27nm Samsung Toggle NAND, and is capable of max sequential writes of 168+MB/s in contrast to it's SATA III 64GB counterparts. It's used 16,879 PE cycles for NAND that is at best rated at 5000PE cycles.
This drive will write for much longer still, but at some point in the near future, it might only survive a power-off period of a week, or perhaps 5 days. I'm not really sure yet.