I think you guy will find this interesting.
http://www.amamax.com/acaan2safldi.html
SDHC cards have a very specific issue all with SSD devices in general.
They have a limited time of persistence for there memory.
To be precise the memory itself has a life expectancy of the data stored in it of ~10 years.
MLC (multilevel chip) technology goes between 5-10 years in endurance (IE keeping it's charge). SLC (Single level chip) technology has one of 10 to 40 years depending on size (the higher density the short life span of the data). This is one of the issues of NAND flash, is that it has become a poor quality device in terms of durability (IE you can't write more than 1000 times) before failure and the state of your data is questionable often as well.
Example
Samsung SLC NAND is ten years so is there MLC by the way (Samsung is better quality) 100000 cycles WITH ecc (it requires error correct encoding to meet that number of cycles). The SSD cards last 10 years because they are the same technology.
NOR flash on the other hand
Macronix NOR flash for example is at 20 years.
You are probably now think "it will change so .. whats the big deal?" How do you know what will change and when it will change on your SSD? I have a system that's over 10 years old that boots an old version of linux. These are things you should keep in mind when you buy stuff.
The important thing is KNOW the technlogical limitations and keep your data and system safe. I'm right now attempting to read 10 year old CD's with limited success (yep securely borked up).
Oh and some flash is rated for 100years so 20 years is short for NOR flash.
Cyb