I'm currently embarking on a reading of the Digha Nikaya, so I thought it timely to ask a question based on something I once heard (sorry I can't recall the source).
I've heard it said that as a general rule, the longer the sutta, the less likely it is, that the sutta is an historically accurate sutta.
Reasons for this include:
* Increased likelihood of it being cobbled together from various disparate sources
* Increased likelihood of additional details being added posthumously by those who never met the Buddha
* Suttas started out shorter, and over time expanded in length (compare the length of the average Samyutta Nikaya sutta to that of a Mahayana Sutra for example)
Do you think this is an accurate rule-of-thumb (if so, how accurate?) or are there other rules-of-thumb which provide a better pointer as to the accuracy of suttas and their legitimacy as artefacts that genuinely reflect the word of Buddha?