Between us, my partner and I are waiting for 10 different 2nd class letters (pokemon cards) that were all posted 7-10 days ago. At what point should we be concerned that they haven’t arrived?

I’m not sure how long I should be expecting these to take to deliver.

Super confused because this hasn’t happened to me before, even in December. I know some delays are expected around this time of year, but the RM website doesn’t list my area as one where particularly bad disruption should be expected. They were from 10 different sellers so I know we haven’t just been scammed because at least some would arrive by now.