IIRC, this topic has been volleyed a few times, but not recently. Obviously if this sort of planning is a feasible part of someone's prep, then it would follow that a diverse collection of off-site storage opportunities would be the most preferable. In some cases, keeping a box or two of secured items at a friend's/relative's house along a possible route would be the most economically sound approach, while in other cases where such convenience may not be available, one would be compelled to lease the space needed to maintain that route as an option for future use.

I guess my biggest concern of course is the level of security needed to assure that such a cache would not be vulnerable to scavenging by others before I could get to it. For me, the most ideal stash would be one no one else knows about and is highly unlikely to discover, yet relatively easy for me to access should the need arise. In a big city, such locations could be quite plentiful, depending on to what level you are willing to investigate to find such locations. In rural areas, it is simply a matter of grabbing a shovel and making a midnight stroll in a general location I want to stash for, along with a gps with information that will later be transposed to a map (Captain Kidd approach).

Ultimately, I suppose a good deal of my equipping effort during bug out will likely consist of scavenging other people's stuff, should I need it. Macgyver meets Escape to New York I reckon.