I don't believe that coils will "never fail", I sold roughly 125 echo pb-210 and the Pb-210e a year for about 8 years qas a dealer.. (They were the most loved item by theives, and if you ran them over with a truck they were done).... I can not remember EVER having a warranty with a Echo pb-210 coil. I have seen chafe the wire to the kill switch and ground out the coil, or break the inside guts of the switch to do the same...
I had maybe 10 to 15 echo's (blowers) in the shop at a time for repair in the shop, I only kept one coil in stock for repair, and only a used for trouble shooting. I would change coils for mech damage only, ie.. dog ate of spark plug wire, dropped unit and coil is cracked...
I am just saying it is rare....be VERY VERY suspect if someone trys to sell you a coil for a problem..
Good Luck,
Friiy