These things have a life of their own, meaning that if you don't inoculate, some spores will blow in eventually, and if you over-inoculate, the weaker ones will die out. Inoculation is really a sign of impatience, that you want to get the stuff to break down quicker and get the soil life humming. I got 7 dump truck loads of wood chips last month, and have been sporadically throwing blender slurry on the piles of any mushrooms that I come across. A couple wet rainy days after one inoculation, that pile looked like it had a snowed on it, the hyphae was so thick. And two days later, it had all disappeared into the pile.
When you have big piles of rotting wood, all is right with the world.
The trick is to inoculate the roots, this is where mycorrhizal activity is most beneficial. We usually inoculate when we are adding trees to the orchard, putting in pollinator attractor plants and when we make a new vegetable garden bed.
If we have to dig an area, as in prepping a new vegetable bed (our land is chock full of rocks), then we inoculate once all the disturbance is over since we most likely destroyed the living habitat of the hyphae that were there.
Other than these instances, we don't do any disturbing of the soil strata when we plant, if we find hyphae around the planting hole then we don't add inoculant since the living hyphae will come in and attach to the new roots from the area surrounding the new plant.
Mycorrhizal fungi seem to do a great job of spreading as long as you aren't disturbing their habitat. Our testing shows that we can expect a spread rate of 2 feet per month of leaving the soil undisturbed.
Our hog pastures are only disturbed by the hogs rooting and I have noticed that the hyphae come back rather quickly into these rooted up areas once the disturbance is stopped. (we rotate our hogs so the pasture they were on can recover between grazing periods)