Printed threads and snap connectors are nice, but M3 bolts and nuts are more robust and look dope. They also make the model easier to design and print, since you don't have to worry about tolerances as much.
STEP files here: printables.com/model/548770-master-spool
I just use it to save a bit of money. Refills are a few moneys cheaper and it adds up. This one will pay for itself in about 3-4 months.