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#11
It is not that they fail. They just disappear. There are a variety of circumstances under whish that can happen. I don't have a complete list though.
Hmm. Now that you mention it, 2 of my restore points have disappeared since I started this thread (and a manually initiated one has been added). It does seem to have anything to do with size - I'm nowhere near the configured space. Is there a maximum count of restore points specified somewhere?
Sometimes attempting to use a restore point fails. This may happen because of some conflicting program or perhaps a permissions issue preventing the replacement of some file.
Sometimes (instance reported recently) using a restore point can render a system unbootable. (I would guess there's some underlying corruption leading to that sort of failure)
Third party AVs can stop System restore to finish restoration and even it's creation as Avast did to me few month back when I was using it.
AS for restore points disappearing, some updates can delete them as usually happens with insider version which turns it of completely. Anyway, I don't rely on them too much as they are of limited use, Full system backup does much more.
The number of restore points you can keep is determined by the size of the shadowstorage. Figure each restore point needs appr. 1GB.