3D printers with multiple extruders (or multi­headed printers) are common in the desktop fabrication community, but are primarily used for multi-­color or multi-­material printing, using only one extruder at a time. What if these multi­headed desktop printers could also be used for simultaneous parallel printing? While this is a relatively unexplored direction, we argue that it deserves further investigation: a flexible, robust, and affordable parallel printing ecosystem could significantly reduce fabrication time for many applications and further enhance the value of desktop rapid prototyping. We propose a research agenda to explore the development of a parallel printing pipeline, and summarize our observations from a preliminary investigation of simultaneous extrusion. We hope this vision will encourage and guide future research in developing hardware, firmware, and slicers to facilitate parallel 3D printing.