Having an organised bitz box or collection is the easiest way of ensuring you don’t lose all those valuable bits and pieces. They can be sold or traded to help build your collection, they can be used for conversions or even be magnetised to provide weapon and accessory swaps.
A visit to the local hardware store netted me a few storage boxes. Having filled them both, plus a cheaper version I had to go grab another for my Necron army.
Having everything separate and in containers which won’t mix when the box is moved around is really important. That way you can label the boxes and know what you have with a glance.
So don’t throw out all those extra bits and don’t waste space storing almost empty sprues!