I have purchased everything I want out of the New Year Shop (all available years) and still have over 200 tokens......is it worth it to hang onto them?

If you still have the tokens in items just sell them, otherwise there isn't much to do? You can make a board in the Advertising forums selling the currency and people can request specific items, but otherwise holiday items don't sell well in user shops.

I always leave certain amount of currency in vault for next years. If I can't/don't wanna play much then I can still get all the items.

I prefer to hang onto my extra currencies too. It's nice to buy something if you really want it at the start of the next holiday.

Some of the items from older years sell for more than the price that the NYT would cost to buy them.

I love hanging onto them to give as gift, or buy shop items as gifts. Also, as had already been mentioned, hanging onto them to purchase next year's items in case I'm too busy or ill to get them next year.