You're not alone! I think about it too, I'm sure every fish keeper does. When I first got my 75, it was intimidating, after awhile the 75 seems so small and easy to manage and now I'm planning on building my first plywood tank. It's going to be huge (huge to me is bigger then I ever had before). The total water volume with sump will amount to 300+ gallons. That's a lot of fricken water! I think about what could go wrong every single day. I think that's the key is to be a few steps ahead. You know what could go wrong, now do what you can to prevent it from happening.
IMHO plywood tanks appear to be the most strong and durable, so I feel very confident that if you build it, it will last. The nice thing about a plywood tank it's like building a stand and you have many options to make it as strong as possible. I think if you take care of a glass aquarium, it should last for a very long time. I inspect my glass tank often and everything holds very well.
An ounce of prevent can go a long way. A leak or bust doesn't just happen out of no where. Silicone and Rubbermaid are your two best friends in this hobby. As long as you have those two, doesn't matter if your tank explodes. I also have a plastic shower curtain underneath the stand and all around for water spills.
I've seen some tanks that look like crap, if you don't take care of it or if you bought cheap at a swap meet or off of CL, then expect the worst. I can't believe the people on CL selling dirty nasty broken fish tanks/stands.
I did happen to get an old style 55 glass tank (no brace) off of CL, it has 1/2 inch glass (sweet). The silicone looks worn but I did the water test and it's a beast. I still plan on adding more silicone just to be safe. The glass is stained, tried everything to get it off but nothing works. You can move your finger over the glass and it's smooth so not sure what the stain is from. It will eventually be turned into a sump.
My goal for the future is to only use plywood tanks, glass is becoming obsolete.
