warn them!
I cried the first year my mum decided not to bother (I was 21). Big, sad, fat tears of unhappy.
Of course i could have bought myself one. Not. The. Same. Thing. At. All.
wer have a refillable tree-shaped one with drawers from M&S, but i don't think we'll bother this year because grinder will miss over half of advent and I'll miss the last week.