StringSubstr()'s limit

 
Is there any limit in this "string StringSubstr( string text, int start, int length=0)"? I read the documentation, but no answer.

"length=0" means I can extract starting from the given position and up to the end of the string. But when I do so, it always cut the tail of the string, the maximum character seems 4K only. If the string is longer than 4000 characters, its tail will be cut down. When I change another computer, more than 5K will be cut.

I have added my computer's RAM to 1.5G, not helpful yet.

Am I doing something wrong?

Thanks in advance.
 

Why do you need such long stings?

 
I need my EA to export a document to analyse something, this document will accumulate daily, so longer and longer.
 
DanceWithLions:
I need my EA to export a document to analyse something, this document will accumulate daily, so longer and longer.

Try to write / read it line by line... That would be a more "normal" method...
Reason: