My Limbo Portals have lasted more than one use. In the combo I mention above I used them at least twice on two separate turns in a row.
Maybe I am misunderstanding how Gather works but I play Gather right on the Portal. They seem to go through the Portal and in the direction that I want them to go. To be honest I thought that Gather had to be used with the Portal when I first saw it. Seemed like the perfect combo to me.