Tanks usually give plenty of warning signs as stated above, and if the do start to leak they usually will drip/weep which will give you some time to react. Being the eagle tanks are 34 years old made of mild steel I keep them about ½ full so there is enough room in the other tanks if one starts to leak. Also polish/clean the fuel, use additives, and try to turn the fuel every 1 to 2 years.
Fuel tanks are not usually made of SS but mild steel as SS needs to breath, hard to weld, heavy and expensive. Aluminum is usually used when replacing tanks which I don’t think is as good as mild steel. If the Eagle tanks go I plan on replacing with multi smaller plastic tanks and usng the larger old tanks as frame work for the new tanks.
Anyway if you are concern then take some positive action.