Regardless of arbitrary limits, the real constraint is that any texture that exists in a loaded array is also loaded. Therefore you can introduce a huge memory bottleneck by loading textures unesscarily.
A good practice would be to create arrays with texture that have a high probability of being loaded at the same time anyway.
For example, all of the foliage within a single biome/level could exist in an array. But putting foliage from another level or biome into that array would cause it to load even though it might never be on screen.