I was hoping that someone would reply who has some practical experience with this, but I guess I'll just reply from the theoretical point of view.
First, when the alignments were performed, was the vehicle "out of spec" and had to be adjusted? If that's the case, once irregular wear starts, it can be difficult to get rid of!
If the alignment was "in spec" how far off of nominal was it? IMHO, vehicle manufacturer's alignment tolerances are too wide. Not the nominal value, the allowable range. Modern radial tires are especially sensitive to toe in and don't like to be off the nominal value by more then 1/32" PER SIDE. (I think that's 0.06 degrees)
There is a vehicle setup parameter (basically nonadjustable) called "Ackerman" which is the amount the toe in changes when you turn the steering wheel. This is to compensate for the tire on the inside of the turn needing to turn in more than the tire on the outside. However, the amount varies with the speed of the vehicle and the radius of the turn, so there is one optimal combination of speed / turning radius. If you drive in such a way that you are far away from the optimum (outside the box), you are in essence dragging one of the tires through the turn and that causes irregular wear. Examples of what is NORMALLY driving "outside the box" are:
1) Frequent low speed turn ins when you turn the steering wheel as far as it will go, like when you pull into a parking space, especially if you only drive short distances between these - and of course the faster you 'whip in", the worse this condition is.
2) Freeway on ramp / off ramp cornering, like the 270 degrees loop arounds, especially if you drive short distances between these - and of course the faster you go, the worse the condition is.
3) Many turns compared to the miles put on. I like to use "Turns per Mile", meaning how many substantially 90 degree turns do you make divided by the miles you travel. I consider 1.0 per mile to be average. BTW, I don't count it if the road wanders a bit, only if I have to make a turn that is the equivalent of a turn at a city traffic light (However, I count freeway on / off ramps that loop 270 degrees as 3 turns.)
Also the inflation pressure has a major effect on the rate irregular wear appears.
Hope this helps.