I'm not sure how long it took, but for a while the instance had crashed. For some reason the Lemmy photo upload service took up 150GB of free space and hence the server crashed because of it. I'm not sure about the possibility of recurrence as I don't know the exact reason.
For this reason, you can follow our Mastodon account, which I have just opened, to follow or report possible crashes.
https://mastodon.world/@lemmynsfw
Yeah I asked this on lemmy repo after this comment. It seems like I really can switch to object storage with release candicate right now. There is 130gb of free storage on the server so I will wait for stable version until it fills up. Hopefully they releases stable in the mean time.