Don't know who said it, but someone pointed out that after three days without food, people would steal it (shorter time periods for those without a conscience) and after seven days they'd kill for food (again shorter time periods apply).
I think the above is probably true, but then I don't have a huge amount of respect for homo sap (yes, I are one - I think).
I presume therefore that within a three month period of no functional infrastructure the population of the earth would have been reduced to it's highest self sustainable population. I'd guess roughly 300 million. Somehow I don't see myself making it into that group. With only one percent of the current population surviving a three month fiasco, I suspect I would be one of those to perish early (probably in a confrontation with someone more heavily armed). Therefore, I am not doing any significant preparation and will simply become one of the struggling throng whenever it (world wide enduring disaster) occurs.
Unlike some above, I do expect it to occur, and most likely in my lifetime.
Be blessed!
Not all those who wander are lost! I am not. Yet!