First, you should verify whether you had late blight or some other disease. Late blight typically doesn't overwinter in soil or dead plant tissue laying in the garden. Late blight typically overwinters on potato tubers or "live" plant tissue. However, there are late blight mutations that recently have been found capable to overwinter in garden soil or decomposed material. So again, you should have a lab test run to confirm whether you have late blight or another plant disease before determining what cultural practices or chemical applications might be appropriate to address the disease.

Where would one get such a lab test and how much is it
likely to cost? I have a big problem with what I think
is late blight but never thought of trying to nail it
down closer.

if you have space at all, why don't you build another raised bed or two and rotate the tomatoes from year to year between the two?
If no space, make sure you clean up all the debris from last year, and mulch your plants this year with shredded leaves or etc to keep the splash from the soil from coming up on them. You could also spray the ground real well with Physan 20 a week or so before planting just to be on the safe side.

Another thing to do is add corn mill when planting, a hand full mixed into each hole or in your case you divide a 5 lb bag and put half on each bed. Its suppose to add beneficial bacteria to the soil.

You might to look at this thread I posted a couple weeks ago, particularly Carolyn's response. She recommended a regiment of fungicides to ward off late blight. Places that are hot & wet are prone to late blight. Ultimately, late blight will probably still get the plants, but you'll get a longer season using a fungicide.

Here is a link that might be useful: Disease Resistant & High Yield

You might to look at this thread I posted a couple weeks ago, particularly Carolyn's response

*****

But the response there was not specifically about Late BLight.

There's Early Blight ( A. solani) and Late Blight ( P. infestans) and they are two entirely different diseases and either one can appear early or late in the garden.

So before deciding what to do about what you thought was a Late BLight infection I think it would be a good idea to know which blight you have, or indeed if it was Early or Late Blight and not one of the more common foliage diseases.

Can you describe the symptoms in detatil here so that folks can have a shot at trying to Dx the problem?

And it would be very helpful to indicate where, geographically you grow b'c Late Blight (P. infestans) is still somewhat regionalized.

You also might want to consider Googling some tomato diseases, either by doing it straight out, or by going to Google, selecting IMAGES and entering your search words.

Since Early and Late Blight and all the common foliage diseases are acquired initially by airborne transmission, clean up of the soil in the growing area really becomes a seconday issue although it might help splashback reinfection from spores and bacteria that have been shed to the gound in a previous year by infected plants..

Carolyn