What's happened to the discount for unlocking the rune slots? We have had the unequip discount but not this one for a while

It's only been a little over a month. Last one was toward the end of December.
Other sorts of discount events have happened more frequently, but it hasn't been all that long in my opinion.

@sansot that depends on how many decent monsters you have acquired in the meantime. Plus how lucky you have been with locked slots. But cheers