Yeah SD cards aren’t the most reliable devices but they do the job. At the same time though all Solid state devices have limitations so I think your going to have problems no matter what you choose. Even standard hard disks can fail after a couple of years
I would love to see a Gadgeteer device with a larger storage capacity but the price rises rather steeply with these chips. I had a look a while back.
At the end of the day all I can suggest is buying a reliable SD card brand and model and ensuring you make daily backups to another device such as the USB stick. Log every time a problem occurs on the SD card to give you an idea of any potential problems with the plugged in SD card and try to predict failiures