We learned from Odin that there are laws that govern the progression of time in relation to space. Altering the future is easier than changing one’s past, which is more than mildly difficult. Overcoming the inertia of an event to remain as it originally occurred requires tremendous energy, will and a measure of simple luck.
The larger, more significant or more energy in the event, the more inertia it has to stay the same and the echoes caused by a temporal event are proportionately greater than the span of time that was bridged. If centuries are bridged, echoes begin far, far in advance. We see that the energy echoes happening in the day before the events at Demonreach allowed Harry to determine that the spell was being cast that same day or hours around that time.
Now consider Little Chicago. If it had not been fixed, it would have exploded with tremendous energy. It would have killed Harry, so it was a significant event in his timeline. Therefore, it is a large, significant, energetic event with an equal amount of inertia working to keep it happening the same way. Therefore, if a time-traveling Harry went back into his own past to fix Little Chicago, which occurred 6 years ago in the Dresden Files timeline, at the very least we should have been seeing echoes 6 years before Proven Guilty, right? And the further in time we get from the fixing of LC to when we see TT Harry make the trip, the early the echoes should have started.
In Cold Days, the echoes we saw from the events at Demonreach included an energy building up, like a steam boiler, that was going to explode and take out the midwest. I'm not sure what kind of echoes to look for from TT Harry stopping the explosion of LC and his own death, but I can't think of anything that would fit the bill.
Does this sound a death knell for the idea that Time Travel Harry fixed Little Chicago? Can anyone think of potential echoes which prove that Harry did travel back in time and avert his own death??