The original packaging preserves one kind of value while preventing another kind of enjoyment.

Keeping something sealed protects its resale value and its condition, and it costs you the entire experience of using it. Both are real values, and they cannot both be had. The difficulty is that the preserving choice tends to be made by default rather than decided, so years pass with the box unopened and the question never asked.

Pick one thing you have been keeping in perfect condition and decide deliberately which value you want from it. If the answer is that you will never sell it, that is a good reason to open it this month.