Valor Wiped Out Unexpectedly
It wasn't made clear that the unspent valor would be wiped out at the end of the period - I had been saving some to spend at the start of the next cycle. I falsely got the impression that the timeout referred to the the number of items that one could buy. Otherwise, I'd have bought more shards instead of waiting for the price (but not the valor) to reset.
I know that that might sound greedy - expecting one to reset, but not the other, but I thought that the purpose of the buying limit was to space out purchases, with the countdown referring to when one could buy more. There was no indication that I would have to spend valor by a certain time.