I guess there are actually few ways to permanently fix the spring in place during construction....given the size. Especially if they are a part that will age and therefore need consideration for replacing during the coupling's lifespan. I imagine the size, style and strength of the spring is in direct relation to the size/strength of the magnets... something that is already a compromise. A reed style spring for example - which would be much easier to 'fix at factory' would probably be too resistant for the magnets.
I imagine with the relatively small number of steps in the construction process, that an additional process of permanently fixing the springs in place at the factory would probably cost more than supplying every coupling with spare springs. In turn, the cost goes up. In consideration of Dave's previous comments with regards to the price difference between the single and five pair packs, I think cost is a big factor for such a small product.
Just a thought. Could and most probably am wrong LOL.
I'd be interested to know if Dapol have considered feedback to offer spare springs, as I'm informed other brands do?
Regards
Lee