Well, I can only tell you what California requires. Probably won't help much with your Texas accounts, though....
In the California Unclaimed Property regs, all documentation for escheat (meaning also records for why we didn't escheat an account - like the dormant account re-activation form) must be retained for 7 years after the report's due-date.
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Just a lowly 1st Year Law Student ("1L"), so don't take anything I say seriously!