I try not to hoard materials but, darn it, they come in handy sometimes.
As a parent, we often get instructions from teachers to send materials to school so the kids can make 'X'. It never failed that I had just recycled the thing that would have been perfect for building 'X' (or had thrown it out if that wasn't possible).
So this year, I've come up with a better system of saving things for future use. For the little bits and pieces, I have a 'Bin of Requirement' (after the Room of Requirement from Harry Potter). It's one blue Rubbermaid tub in our storage area where I can stash interesting materials and packaging for creative projects, science projects and who knows what else.
On a larger scale, we have also dedicated an old shed to be the 'room of requirement' for building materials. It houses leftover lumber, metal and scraps from the previous owner as well as other pieces we've added.
The real trick is keeping enough variety and volume to be useful, without becoming a hoarder and never being able to find what you want because there's too much of it. Especially when you were raised in Saskatchewan and now have lots of outbuildings you could fill...
We've only been here for a year, so we haven't hit that point yet. And we are getting to actually use the materials. For example, our daughter was asked to bring small coloured objects to be glued to the rainbow poster in her Kindergarten room - we easily had that covered with multiple bottle and pill caps. I've also built some handy bridle and halter racks for my barn out of scrap 2x6 and post ends.
What about you? Do you hang onto anything you think is too good to let go, like toilet paper rolls for crafts, or twist ties? I'd love to hear what my fellow thrifty Saskatchewan folk are keeping 'just in case'.