I plant my tomatoes in groups too. I'll have two or three of a variety, I plant them next to each other. It makes mapping out the garden beds a lot easier. I do usually plant 40+ tomato varieties each year. What I do to break it up, so to speak, is plant opposing heights next to each other. INDs go next to DET or Dwarf types, reds by yellows, purple by orange or green, etc etc, again this is to make rapid differentiation between the plants when Ii'm outside. I do tag them with markers in the ground as well as make maps, saved in the computer and several printouts of them go on the office wall, garage wall and a set for the living room table too.

I think what you are saying is that you don't know if a specific location will be ideal, or whether it will be invaded by critters or mildew or blight, so you plant the same variety in several different locations to improve your chances of getting at least a few of each variety. Right? If I'm hearing you correctly, that makes complete sense. I've never had the luxury of that much space for my plants. One, crowded tomato bed was all I ever had--and now I don't' have enough sun to make it worthwhile anywhere. Though I love my shade. It's nice to be able to go outside without a hat and layers of sunscreen. I'm a redhead, so I have to be careful. Shady flowers are my focus now.

Martha