The situation described is not an issue for me because I water the friggin crud out of my plants. I water so much that lots of water comes out of the bottom of my soil pots when they drain. All that water would wash any accumulated salts out if there actually WAS a chance for them to accumulate. Now, some people do not believe in watering that much. There are theories about how just a little water is good for herb plants; theories like increased vigor and root size and the effects of stress and drought on potency. Of course, I have respect for those methods and I see the good but I think lots is better because I believe that giving plants all they want lets them grow all they want and that stress is bad and my root balls max out in rather premium ways and potency can be, and will be, had in friendly ways.
The boys that use drought usually wash their soil every week. Which kind of kills the drought if you think about it...
but every week is what I've heard. And I think they wash it a few times on those occassions (maybe 3 or so)<<that usually means about one inch of water. In comparison, I feed an inch of fert water twice every time I water. Sometimes three times. I like to do it every day. and I often re-water with the stuff that has drained out<<not indefinately, of course. and The soil has to be great for this to work right. nice and light. loamy. porous. For seedlings and big potted (2 1/2 - 5 gallon) commune partners I do it more than once a day.
An inch of water means that you pour on enough so that it would measure an inch deep over the whole surface of the soil. and then you let it drain so there is no more standing water on the soil.
and if you are rinsing or watering like me, then you do it again; repeat as many times as you want.
When I had a problem with nutes once (i put on a couple of tablespoons of ashes and almost killed the plant), I washed the soil about ten times with two inches of water and the plant was fine after that. so, that shows what lengths one can go to and it shows that they work.