@drhs07 - While I understand that you want to maintain the good relationships that you have with suppliers, I think you should consider your colleagues' suggestion in switching to a cheaper supplier.
Although I am not familiar with your situation, saving money should be the number one concern of your procurement logistics. You would be surprised how much money can be saved over the course of a year by choosing to buy a particular material for just five cents cheaper.
If you are worried that these new suppliers can not be trusted to deliver your materials in timely manner, I suggest that you do a little online research to see how good or bad their services are. Once you determine that they have a good track record, test them by seeing how good they are at fulfilling just one order. If they meet your standards, I say continue doing business with them.