If you are frequently changing your PCB manufacturer then you should consider changing your approach. Instead of working with a new manufacturer for every order you must take advantage of the benefits of working with a single manufacturer. Most of the electronic equipment manufacturing companies ensure that they find a regular supplier of PCBs because they find it to be one of the most convenient approaches of sourcing your PCBs.
In any electronic manufacturing company, there will be several responsibilities and roles. Sourcing PCBs is just one such role and you will cannot just limit all your attention to your PCB manufacturing company. If you do not have a regular supplier of PCBs that is what exactly would happen. You would be busy spending all your time searching for a new manufacture and try to find a better quote. You would unnecessarily be draining all your energy to the PCB manufacturing company. You do not want to make this mistake.
When you are screening your PCB manufacturer you must keep in mind the fact that you are not looking for a one-time supplier but you are looking for a long-term supplier of PCBs that you could consider for all your current and future need. Only if your supplier is highly dependable and only if they are offering you the best quotes you would be able to stick to the same manufacturer. Or else you would be forced to look for a different service provider. As you could see clearly, whether or not you would be able to stick to the same manufacturer for all your ongoing needs will depend very much on your choices.
After taking into account all these factors if you manage to spot the best suppliers of PCBs you do not have to worry about looking for a better supplier for every order or when you need to stock your inventory. All that you would need to do is to send your requirements through a single email and the rest would be taken care by your regular manufacturer. Or else you would have to go through a long and windy screening process and the boring quotes comparison process.
When you work with a single PCB manufacturer for all your ongoing requirements your manufacturer would show better understanding of your needs and specifications. This would enable them to deliver better quality PCBs. You would face fewer issues dealing with your manufacturer and fewer headaches in terms of delivery timelines. There would be a better working relationship whenever you work with any PCB manufacturer for a long term. All these need to be taken into consideration when you are looking for the best PCB suppliers.
Most customers do not realize that they are likely to spend more money on their PCBs if they keep changing their suppliers. Each new supplier will charge you an initial setup fee when you signup with them. To avoid multiple order or account setup costs, deal with a single manufacturer.