Rule of 3 is great rule, especially when you consider the fact that when SHTF very often nothing work as you planned, so it make great sense to be sure.
I also pay great attention to be as lightweight as I can, because it means a lot in some situations (usually life and death situation).
Best choice is usually compromise between “be sure” and “be lightweight”. Also good thing is to have knowledge and skills to use what you have (or what you can find) around you.