I use a pair of double-hinged pliers (similar to these) with a slight curve at the tip to help work the coils free. (Carefully!)
I recently changed my plugs and found them in good shape. I see no reason beyond the regular use of crappy gas to change them before 15-20k miles.
As for not using a plug that's been dropped - Amen. Dropped 6 inches onto a work bench is one thing. But, on the floor? Trash can it. Ceramic material is not something
you want flying about atop a piston top. =)
More on gapping from NGK themselves:
" If it is necessary to widen the gap, do so with a tool that only pulls back on the ground electrode without touching the Center Electrode or the porcelain. To close the gap on a plug, gently tap the plug, electrode first on a hard surface. NGK doesn't recommend adjusting the plug gap more than .008" in either direction. Beyond that slight adjustment, the ground electrode and Center Electrode won't align properly, hindering spark plug performance and drastically reducing plug life.
•Due to the fragile nature of their electrodes, special care should be taken when adjusting the gap on Fine Wire plugs.
•Gapping should never be attempted on Multi-Ground plugs. "