Louis,
I guess the question I have are you planing on a large number of images opened at the same time? I've worked with large numbers of 14MP images during stacking, 800+ not including the calibration files without any issues. I've also worked with Hubble images at sizes of 15000x15000 without issues. Even some very large mosaics, larger then the Hubble images. Tasks may take more time to complete but those are huge images and my swap drives stay very busy. My computer is a Windows 7 machine with 16GB, a 6 core AMD processor and no SSD.
I don't normally have more then one instance of PI open at a time but the computer is running many other tasks such as video processing while PI is running. I find core management on my computer essential. If I know I'm going to be working with huge projects I'll reserve a processor core or two for all other computer activities. This way Windows or other programs are never waiting. Nothing worse then a mouse not responding or a web page not opening because all cores are at 100 percent. While working for hours at such high processing loads I have never had PI crash or freeze completely. I've never had Windows crash or lock up either. I have had some minor third party programs crash but PI and Windows kept working.
The other option of course is a computer that can handle more ram. Servers systems with 32GB,64GB or more RAM are not that uncommon today. They also lend themselves well to running Linux for better memory management.
Mike
