How long may distance be between transcription and translation start site?

Ensembl has annotated transcription and translation start site for 85% of all human genes. For large fraction of these genes (33%), this distance is more than 1,000bp. [PMID: |Prakash1 A.,Tompa M., Nature Biotechnology, 23, 1249 - 1256 (2005)]

This paper is definitely a very good introduction for 'Discovery of regulatory elements in vertebrates through comparative genomics'.