Evergreen trees usually don't last long, and are really too thick for fish to get into the limbs of. Usually what happens is the branches rot off and leave just the trunk of the tree...and if you sunk a bunch of them in one spot, you pretty much made a glorified stake bed. I've had better luck making those out of pallets and tobacco sticks.
On the Jim Duckworth video I had, he took long sections of flex plastic pipe, and a long piece of PVC pipe...and put them in a 5 gallon bucket and filled with quickcrete. When it was all said and done, it looked hideous and resembled a huge spider with long legs coming out of it and arching over but after you sank 3 or so of them in a spot, it made a huge brushpile that would last your life time. And up until Side Imaging came along on sonar, you couldn't pick them up on sonar. Now you can.