If you look closely you can see the original four posts and how far the back ones moved. They are almost under the porch. You can also see that my husband enlarged the bed for my gardening pleasure.
To answer a few of yours. I put the sweetgrass in window sills and in my jeep. I keep one in my office as it soothes unruly students. I have one on the window sill next to our bed and it helps me sleep. They last about a year or two. My mom got me one for Christmas long ago and I loved it so much that I bought a few plugs, my sister gave me one, and planted them near our pond. They love moisture. This year was very wet and it grew like crazy.