What is the reasoning behind the oft given advice never to plant tomatoes in the same spot? I have just planted mine in the same spot I've planted them in for the last 3 years and they have always done exceedingly well. I expect another bumper crop this year. I always dig over the soil really well each Spring and add plenty of homemade compost. However, is there something I don't know?
Two reasons: - pest / disease buildup - nutrient requirements (sounds like you are taking care of this with the addition of compost) but if it ain't broke, don't fix it. :D
The main problem is that you risk getting Nematodes in your soil which will eat the roots of your tomatoes and render the soil useless for a few years. They are very hard to get rid of and will destroy pretty much any Nightshades like potatoes etc...
