Depends on how the scene refers to the VAR package. For most content, say clothing items, looks and so on it refers to "latest" version installed. For that kind of content, updates are usually just minor bugfixes or improvements and therefore are not expected to break existing content. In that case downloading a new version (or using the helpful update button in VaM's Hub-browser) and deleting the old one will not break the old scene.
HOWEVER, plugins are usually refered to as exact versions. That's because code changes could easily break old scenes. A plugin might behave compeletly different, add or remove features etc with every version. There are well-made plugins, such as those by AcidBubbles (or myself
) that
try to be backwards compatible. Although sometimes the effort needed to stay backwards compatible just doesn't justify the benefit. If you have an old scene that uses for example an old version of LogicBricks, you can open your scene with Notepad++ (or similar text editor) and search&replace all occurances of the package name / version. Obviously make a backup copy first. Then reload the modifed scene and make sure everything still works.
However, since plugins are usually rather tiny packages, it doesn't matter if you just keep all/most of the versions. Ok, maybe Timeline is an exception because that has 100 or so different versions by now. A good strategy for Hub-hosted plugins can be to just move them to a different folder outside of VaM and then have VaM's Hub-browser automatically re-download those you actually need for the scenes you got installed. If something is still missing...because a particular version wasn't on the Hub...copy them back from the outside folder)
Note that creators can override whether to refer to latest or an exact VAR version. Doesn't imply that creators know what they are doing when doing it
In an ideal world VaM would suppport major and minor versions, so creators could tell VaM whether a new version is safe to automatically update.