I heard Sir James Galway play the Cimarosa with his wife a few years ago. The double cadenza was brilliant - they sounded like one instrument with all the tempo changes perfectly synchronised.

Wow.... I bet that was amazing!

I guess that is one of the advantages to being able to practice together A LOT! Even I noticed that with my flute exam, being able to practice a lot with my accompanist - he's a friend and my piano teacher so we had lots of opportunity - but can you imagine how good you could get at playing together with someone you live and work with and are married to?? Cool.....

*needs to find me a pianist husband, lol*