Adequate stress test for a 125g?

So I have a standard 125g tank (72x18x24 I believe) that I traded for on Craigslist. I was assured that it would hold water but I'm filling it as we speak to stress test it. Of course I won't know how weak it is literally until it breaks but what would you say in an adequate length of time to keep it full? I have a couple months before I'll have the equipment to set it up so I have a lot of time. I was considering just leaving it full until it needed to be drained, cleaned, and setup as a salt tank.

What do you think? Just filling it to the brim for at least a month good enough? Less time? More time? Or is there something completely different I could do?

Big Mike said:

Yes level is very important!!

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Yeah first thing I did. Unfortunately it seems my floors aren't level lol. The water is just barely leaning to one side so it is at the brim on the right and just under on the left. The level doesn't show it being too far off so I left it.

So far it is holding like a champ. About another month of hoping it doesn't pop XD

Rbishop said:

or a month of it being twisted and more stress being applied....

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I don't believe so. I could be wrong as I definitely don't know all about it but it is leaned to one side, not to a corner, and not front to back but side to side. And the water level is less than a quarter inch off over 6 feet. Either way though unless there is a way for me to stabilize it on the stand it will be exactly like that once it is setup since my whole place has that slight lean and the tank will be in a different room but in the exact same position with same off level.

Rbishop said:

Did you check level diagonal to diagonal? Then you have a problem potentially..

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No I didn't. Can't believe that got by me. How would suggest I do that? I only have a basic foot long level.