Cadillac Repair: lower control arms, control arm bushings, suspension component

Question
Another LCA question:  I understand there are two bushings on each LCA.  
After installing new struts mechanic pointed out that rear bushing badly
worn on left LCA and should be replaced. Said that he did alignment but the
worn bushing prevented real good alignment and accounted for a thump
noise often heard on some bumps e.g. speed bumps. He said nothing about
the other three bushings.  Before getting back to him to arrange the
replacement of that one bushing I'd like to understand a little better.  Which
of the four bushings tend to wear about the same together, e.g. wouldn't the
front bushing of the same LCA be worn as well?  Would I expect to hear
from him during replacing the rear bushing saying "we'd better also replace
... while I have it apart..." and then I'm stuck having to believe him and am
facing bigger expense.  Or on an older car (100,000 mi.) is a worn bushing
something that can just be ignored? Can you give me a little clearer picture
of what's going on, what's advisable and what to expect.  Thank you.

Answer
Lou,
Although control arm bushings (both upper and lower on cars that have both) can wear at distinctly different rates, it is advisable to replace them as a set for at least a couple reasons. New bushings will have a different flex rate than the old ones, which can cause uneven movement and even binding of the suspension component. This is due to both age and manufacturer (material) differences. Then you also have to consider that the real cost associated with replacing these bushings is the labor, NOT the cost of the actual bushings. For this reason alone, I'd recommend replacing them all at the same time.
The suspension system is really a group-effort. It depends on ALL parts working properly TOGETHER. For this reason, I always suggest replacing any part that's even in doubt of not being in great shape.