back to my mac shares go missing

I am traveling extensively at the moment and am having problems reaching my other Mac's back home via back to my mac (BTMM). My issue is that everything works fine for the first few days to weeks and I can see my BTMM computers in the Finder sidebar. However, at some point the only shared computers I can see in the sidebar are those on the local wireless network that I am currently on. All of this occurrs while I am on the same network.

Since I have multiple Macs in multiple locations, I really can't chalk this up to a single network issue back home, so I'm wondering if there is any way to get my shared Macs back so I can access them once again. Turning off BTMM and then on again on my traveling Mac does not seem to help.

Are there any other tricks to getting these connections back?