Thank you for your enquiry.
The ChartView object is quite a heavyweight View object and so you may find some performance benefit in re-using these objects rather than re-creating them. However, depending upon your application you may find that this approach offers minimal benefit. In this circumstance we would recommend code clarity over perceived performance gain. There is no real right or wrong answer to this question however and ultimately it will depend upon your application.
I hope that this helps answer your question.