You could have a server option to have machines check how much real-world time has elapsed every time the world loads and resolve processes accordingly. Of course, they'd have to be constantly working at the same rate, which would be near-impossible to ensure (running out of power etc) and mega-CPU-intensive.
Another way might be to take the average play-time (offline) or server uptime (online) per day out of 24h and use that as a multiplier for processes. By the time you could reach the technology level to make the long-process machines, you'd have a reasonable average.
Erm, no. A better way of doing that is to add machines, such as the incoming Multi Blocks Generators, which require maintenance.