Not thought about the re-assembly side of things - most of the second hand items I have collected didn't need dismantling - they came as one unit. (At the cost of the annoyance of moving it as a single unit!)

I am sure there are different experiences out there, could also be the circle of friends that do a lot of IKEA "freecycling" meaning I do see a higher quantity of re-used items being moved about.

I know that depending on the type of item as well there is a build quality issue - like Kallax shelving, it is a little more sturdier than the slightly cheaper version, and given I started with Kallax, I have stuck with it - Same with the Billy book cases too!

Although, the Diam Cake you can get from IKEA... that 100% is not going to waste, and 100% no one is getting a "second hand" one from me... there will be none left ;)

But returning back! It could be Apples to Oranges, there are so many products, and in my experience I have seen people stick to the same grouping of products as well, which could see re-use more possible than say another grouping (for any number of reasons).

Who knows, tomorrow the shelf behind me might just fall apart and I will be back eating my own words :)