[susan53]

Nightedge - I'm sorry, I missed your question before.

1. No. It's not possible. The present perfect always involves a past to present event and/or a past to present time frame. If the event and the time frame are both known to be finished then the simple past will always be chosen.

2. This is an interesteing example because the time frame is not exact but approximate - it's unlikely that she was engaged to John for exactly five years. So the speaker may well see the 5 year period as coming right up to the present moment - this might happen for example if s/he has only just heard the news.

A : Have you heard? Livia has broken off her engagement to John. (Past event with present result - she's no longer engaged to him.)
B : What??? That's amazing - they've been engaged for ages, for at least the last five years. (Due to the "fuzzy" time frame and the novelty of the news, the speaker hasn't fully registered that the event is now past).

Compare this with :

A : Have you heard ? Livia has broken off her engagement to John.
B : Yes, Helen told me. I was really surprised. They were engaged for a long time - it must have been about five years.

By now, B has clasified the engagement as a "past event" and therefore naturally chooses the simple past.