That's really unfortunate about the tanks!
That seems like bad luck for leaks to me. I've got a really old 58 gallon tank (40 breeder footprint, with a couple extra vertical inches). I know it's at least 20 something years old (handed from my grandparents to my dad to my grandparents and back to me) and probably hasn't been resealed for at least 15 of those. It is still holding water well, luckily. We tested it thoroughly before setting it up 2 years ago and all the silicone looks in good shape.
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