This will be my third year running my league. I have had only eight teams the last two years. My first year I went with a standard lineup 1QB, 1RB, 2WR, 1TE, 1K, and 1Def. I noticed that there were a lot of pickups and drops that year. Last year I increased my starting lineups to 1QB, 2RB, 3WR, 1TE, and 1DEF. I also increased the number of banch players. THis cut down on the number of pickups and drops. What it did increase was the trades.
I agree that don't force yourself to have X number of teams. Run with whatever you can get.