Obviously, having some review is important. Five years seems quite reasonable.
I think those reviews have to be informed by actual information data. What I think is crucially important is for the information system to collect more data about itself, about what it is doing, so we can really speak and review from a position that is informed by the data.
For example, I would require governments to track how long it takes to search for information, how long it takes to consult on redactions, how long it takes to prepare for sending it out to the applicants. Feed that information regularly to the Information Commissioner so that her office is positioned to come from a very informed point of view in reviews like these.