> Oversize your card so that the card can properly perform wear-levelling
I think this is half of the problem: SDHC does not require wear-leveling at all, I am unsure of SDXC. But regardless, the wear-levelling algorithm the SD card firmware does is completely invisible, from some vendors it might do a decent job, from some it might be a no-op, we have no way to tell.
The only way to know you're getting wear-levelling is to do it at an OS level, e.g. UBIFS stacked on MTD emulation - but there's a bunch of assumptions there which make it unsuitable for SD cards.
I think this is half of the problem: SDHC does not require wear-leveling at all, I am unsure of SDXC. But regardless, the wear-levelling algorithm the SD card firmware does is completely invisible, from some vendors it might do a decent job, from some it might be a no-op, we have no way to tell.
The only way to know you're getting wear-levelling is to do it at an OS level, e.g. UBIFS stacked on MTD emulation - but there's a bunch of assumptions there which make it unsuitable for SD cards.