If the structure has no walls we assume naturally durable or preservative treated timber was used. If so, ongoing maintenance will be primarily cosmetic.The timber in your attached image looks like a dense hardwood and seems to be somewhat protected from the weather. Large size durable species of timber achieve a long life without any maintenance at all (think jetties, bridges and similar structures). However, long term exposure to the weather causes timber to turn grey and produces weathering effects such as surface cracks.

The changes in AS 1684.2-2021 from the 2010 edition are outlined briefly in the Preface to the new edition - see below. You will also find a summary of the changes in an issue of TimberTrader News which you can access via this link https://www.timbertradernews.com/2020/08/19/standard-changes/.