How do you download stuff from NCBI fast?
Answers to this question can be found on biostars. To give you a short summary:


Faster way might be to use the parallel-fastq-dump, as suggested in this answer. I never tested that tool though, my own experience is that prefetch is more stable than fastq-dump command.
In that same post it seems that the Japanese mirror seems faster, don't know if that is still valid.
The reason this is never optimized might be that downloading from SRA is not a task you'll have to do repeatedly, as described here in this post.