Thanks for the reply (and so quickly!).

I will accept that answer, but yeah, it does sound like the end of the road for the factory then. Too bad

Me and a friend have built an almost-megabase in multiplayer. He's the server, I'm the client. My problem: I'm suddenly stuck at <4 FPS, while he can keep playing just fine.

This historically has happened when I as a client am unable to match the speed of the server. We worked around that by ...

Previously announced friend here.

Factorio deleted the original desync report zip file once I restarted the game, but I did have an uncompressed version of it lying around.
Here it is, recompressed. Warning: 100 mb download.

http://www.pvv.org/~andreasd/desync_report.zip

See here as well: https://forums.factorio.com/viewtopic.php?f=23&t=31617

How long does the autosave sequence take in total?
Please upload the log and the save-file.

Thanks for that link. I DO spend a lot of time saving, I feel, but not to the point where it is annoying.
Losing half a minute ...

Me and a friend are running a multiplayer game lasting several sessions. He's the host, I'm the client.
The map we have been building is about 60 MB large at this point.
Our interacting network connection is about 120kb/s (ADSL upload speeds suck), so starting the game takes about 10 minutes to ...