cant speak for the ng series but have worked 3/400's for 14 yrs and the reverser drag links and links to the doors ' the bushes and bearings allways flog out as for the tank panels they are just as bad for corrosion just ask the boys at qantas in melbourne at present repalcing a lwr wing skin due to corrosion. Allways a problem allways will be , just take the overtime and pay off the family home