I’m going to agree with both Brett-nyc & iab → Capacity is key. I would say that almost every client I work with from the major OEM right down to the 1 -2 man design shop really needs a reliable manufacturer they know can handle last minute jobs as easily as jobs that aren’t so pressed for time. Can you take on a moderately difficult part on a friday afternoon & have it ready to ship monday or tuesday? & will it look good?
From your post it seems as you are relying on your 3D printer & a CNC to do jobs. Do you have a back up plan for when a ridiculously expensive tiny part that only seems to exist in the mind of reclusive service people that disappear when you blink, but are totally sure that a burro coming from the peaks of whatever remote mountain top your equipment manufacturer has hidden it for safe keeping… can be yours in 2 - 6 weeks?
As the manufacturer it’s your responsibility to be on time. The due date is the due date & most companies will forget your name if you let them down. Price, quality & expertise have no bearing when your client has to explain to their client why you are late.
Good luck! 