Bash is flat-out not a scripting language. It is a command language. It does not support typed variables, or named parameters, or any number of basic scripting language features. It technically does not even provide an 'if' construct. It's sufficient as a 'glue layer', and the Unix toolchain is nice, but it provides next to nothing in the way of abstraction, and that's liable to become a problem closer to the 1000 character mark than 1000 lines.

My rough heuristic is, "no more than ten lines, nor more than two variables." Yes, that's short almost to the point of absurdity. The only good thing that one can say about Bash as a scripting language is that it's better than csh. Bash is taken seriously because of its longevity and ubiquity, but it's fundamentally limited in what it can express, and it is quite trivial to exceed those limitations.