Freenet feels very similar to IPFS, but it differs under the hood. On Freenet the network itself is the data store, you don't host your own files, you upload them and they spread over the network. If you go offline, the files still remain on the network. On IPFS on the other side you are storing your own files and the network is just used for lookup and caching. Everything on Freenet is also encrypted, so you don't get the content-addressability benefits (e.g. dedup) you get on IPFS.
It'll go to random nodes, and if those chunks have zero popularity they'll get discarded pretty quickly. The exact details would depend on client settings but probably don't matter for a general answer.
For content that is never accessed, you have lifetimes between 2 weeks (bigger than 4 MiB) and 3 months (smaller than 2kiB).
Content that is accessed regularly can stay around indefinitely.
Some of the sites of Freenet are older than a decade and still working well.
To see the actual measurements, you need to run Freenet and access the fetch-pull-stats: USK@lwR9sLnZD3QHveZa1FB0dAHgeck~dFNBg368mY09wSU,0Vq~4FXSUj1-op3QdzqjZsIvrNMYWlnSdUwCl-Z1fYA,AQACAAE/fetchpullstats/537/
