I did, and I see I am in good company: as of this writing, there are 800 upgrades to 64Gb.

I planned (and still plan) to add a uSD card to the tablet, and I will probably use that for multimedia stuff. But a larger SD card should be more reliable than a smaller one, if it is using the same technology: after all, wear levelling is spread to twice the memory cell. Also, it should be faster (it is easier to find a free page to relocate). And the price is not outrageus. Nokia or Apple asked a steep premium for the extra memory... In Jolla case, the option is more expensive than a uSd, but not too much.