Dd is about to turn 16, so our collection has grown over the years fairly slowly but gets reused every year.
Year 1 was her stocking.
Year 2 was a 2nd plastic plate, glass, cup, bowl set with Santa decoration (a spare to her flowers covered set in daily use).
The books and dvds collection started in year 1 and was slowly added to over the years - some have now gone to younger DNieces/DNephews to enjoy but we still have a box that comes out every year here.
She chose a fleece panel on holidays in Canada when she was 8 that I sewed up for a blanket.
She was about 12 when I got her duvet set.
I got a Christmas mug as a present from my landlady, 23 years ago this year. That was my first, and between mugs gathered at Christmas markets overseas, presents, the odd purchase over the years, we now have an eclectic collection of about 8/9 (and have had breakages too over the year).
I got a lovely cream jug with holly on it when we were scattering my DGran at sea - which I saw when roaming shops with DSiblings afterwards (as it was too early to go to the pub in front of our DPs....even as grown adults) and loved as both Christmassy and it also reminds me of her every year.
I have 2 fake trees (the original cheap 5' version I bought in Primark on our first, smashed broke, Christmas in our new house - where we still had no carpets only concrete floors, and the pre-lit 6' Balsam Hill I bought 3 years ago), and a holder for the real tree we buy if we are staying here at Christmas. I only ever put up 1 (although I threaten 2 many years) but probably have enough decorations for all 3.
I only bought a set of garlands 4 years ago for the stairs. But we do a wreath or wrapping in ribbons like a present for the front door for well over a decade now. DH also wraps lights around a couple of trees in the front garden for the same length of time - but is still rejecting any notion of icicles or any kind of shapes in the garden/walls/roof.
I have a few hand towels that are quite old (I think the oldest are almost 20 years old) that I've got on various trips abroad and as presents, that I carefully hoard until Christmas week and put away carefully with the decorations each year. But the apron I was given as a present is much better fitting than my oilcloth type so that lives in the kitchen all year.
I have some cookie cutters in Christmas shapes, but I only ever cut them and never actually decorate any of them, we just eat them plain.
DH acknowledges me as a Christmas nut, I try and slowly introduce things from 1st Dec (fabric advent calendar, dd blanket and 1 mug each), and building up to the full effect by the weekend before Christmas so it's not too much at once for him. But we don't quite hit full-on Christmas grotto levels. One of these years I might. And I also listen to DH on when the tree is coming down (quite often just before or after NY, rather than waiting to 6th Jan, but never later than that).