Reading through your posts, still at the beginning.
Every 5 minutes an entire state backup is performed and it's content is stored on IPFS which provides a hash of that data
How can you be sure that the state backup will always remain available on IPFS if it's not incentivized?
It actually doesn't, it stay long enough that anybody who need to restart can, but IPFS is nearly built in memory management.
Any idea how long it's supposed to remain on there?
It seems to be up for at least a week, I haven't tried pulling anything too old because it's out of focus. If you're building a service with this you might want to store at least a daily snapshot of the state, most of the memory management happens once daily, and even if it was a gig, it'd take ~3 years to fill a consumer level 1TB harddrive.
Could always implement an incentive mechanism to keep selected backups. :)