Coil packs (coil on plug, can they be tested?)

I am wanting to better understand 'coil packs'. I am not getting a warning 'light' yet, but two mechanics have told me that because of the engine 'miss' I'm experiencing that I will certainly have to replace sparkplugs and to do this of course, the coil packs would have to be removed anyway, so which ever fouled plug we find I will probably have to replace that particular coil pack. That, I understand!!
Where I am at a loss, I am being told that I don't have to replace all of them but that I might as well due to the fact that that it will never be more convenient than now to do so. I have 154k miles on this vehicle ('01) but it really runs well and I want to drive it another few years. Do I necessarily need to change the other 7 coil packs if they check out ok now??? I mean, are there ways to determine that the other ones are still ok?? Thanks (Obviously, I'm not a mechanic, but I do understand saving a buck where I can)