<i>walk through the compiler warnings fixing the code until the warnings are gone - never leaving the image.</i><p>To me, this seems like a disaster waiting to happen if you're doing something complex.  When there are bugs in my code, it usually means bad things are happening to my data, my data structures, and the state of my program in general.  When I find the bug, it often seems far easier to fix the bug and start over than it would be to <i>both</i> fix the bug and track down all the consequences and fix those as well, perhaps writing some more code to help with that which might end up with bugs in it... my attention stack was never that large to begin with, and as it gets smaller I try harder and harder to avoid situations where I recursively just have to do this one more thing before I can do the thing I want to do.<p>I did run some of my images for weeks, and one webapp in particular for months.  After the first few days, though, I was always apprehensive about making changes to it, since I couldn't be sure my files were in sync with what was in the running system -- what if I'd forgotten to write a change to a file -- and since my system <i>was</i> running, I couldn't just reload from the file to make sure, since if there was a difference I'd lose the working copy in favor of one I'd replaced.  It was all very nerve-wracking.  In contrast, the systems I had that were written in Python could be changed and then bounced, trading about 5 seconds for all that stress[1], and the systems I had that were written in PHP didn't even need that; changing the file on disk was enough.<p>[1] I do know that I could have done this with CMUCL, but I assumed that there would eventually be a point at which I realized it was all worth it...