Open Goal and Performance periods beyond a year

Summary

Can Goal Plans and Performance templates be configured to be open for longer than a year, traditionally this is done on a yearly basis but can this be configured to be open longer.

Content

We have a requirement from a client where they wish to do ongoing and continuous apparisals without having to have a forced yearly appraisal and use anytime reviews to track progress.  do you know if a review period, goal plan and performance template can be open for an indefinate period and what affect this would have within succession and talent reviews.  Has anyone come across this with other clients?