Length of Sentences

[Eleanor Olds Batchelder]

Isn't there a problem with deciding what is and isn't a sentence, even
before we discuss their lengths?  In writing, sentences are generally
denoted by a period (full stop), but in speaking, it is less clear.
If an utterance trails off with a "and then..." and then silence, is
this the end of a "sentence" or just the end of an utterance?  If an
entire spoken narrative, lasting perhaps 15 minutes, is linked with
"and then," "and uh," "and so," "so then," etc. with each clause
(information chunk) linked to the next in a loose way, where are the
sentence boundaries?  Can we say that the entire story is a single
sentence?

Am I overlooking something obvious?  In what sense is the length
of "sentences" a decidable issue (let alone a cognitively relevant one)?

Eleanor Olds Batchelder