Writing an RFP and reviewing proposals are resource- and time-intensive activities. The costs for writing and publishing an RFP may be significant and may span six months (or more). Given the significant investment involved, the RFP process must be thorough and must be allotted sufficient resources and time.
Sending out an RFP is only the first step in the project: reading proposals, establishing evaluation criteria, visiting reference sites, performing a live test demonstration, and negotiating a contract will all be steps toward a final selection.
Remember that while your project may be significant to you, it may not be to a supplier. Suppliers are under no obligation to respond to your RFP if they feel it is poorly written, a technical "fishing expedition," not properly funded, irrelevant because they have evidence that you have already "selected" a supplier (". . . the RFP is wired for such and such" as they say), or if they believe that other opportunities appear to be better than yours. When they have multiple RFPs, suppliers will be selective and will work only on the ones that appear to be winnable.
Finally, the selected supplier becomes another member of your team and part of your company. Build a supplier relationship based on your mutual understanding of, and agreement with, the requirements and the work to be performed.