Any items that are specifically Holiday - buy them soon.

JLY:
Sweet Sequins Party Outfit
Wintry Weekend Outfit
"Let it Snow" Sleep Set
Bitty Baby:
"Let it Snow" Snuggle Set
Bitty Twins:
Pretty Plum Dress
Pretty Plum Skirt Set

They may be available or even on sale after the Holidays, but it's a chance - I always order this type of outfit first thing.

Next, after the Molly Movie is shown - anything pertaining to the movie will sell out fast. It could be the stage, outfits, dolls, who knows.

Jess is only until the current inventory is available. Once sold out, it's gone.

The above strategy works for me as far as getting items in time for Christmas is concerned.

If the Molly items run out they will be available next year.