So, Chaos Spawn gain eleventy billion fatigue per second in realspace...

How many ways are there to keep Chaos Spawn from overloading and fatigue and dying?

Ecstatic Oblivion and maaaaybe Frenzy seem the only reliable way to keep them fatigue proof for long periods of time. Are there other options?

Stasis field. You could store Greater Daemons in them for millenia.

It's also feasible that they would be able to endure (or at least for longer) in areas where the veil between warp and realspace are weakened either due to some catastrophic ritual or other event. In such instances where the area is bathed in warp energies, it is a given that daemons would fare better in this area.

There was mention in a short campaign description in one of the table top books where a chaos warlord had halt his invasion of a planet when the tides of the warp got low. He had to start building shrines and monuments to stop his demonic allies from fading instead of attacking.

Daemonic shrines, areas of Warp energy...you could possibly sustain them with large amounts of tribues of slaves, or by having Psykers burn themselves out keeping them alive. Those could work. The thing is, Chaos Spawn aren't meant to be kept alive for sustained periods of time, as a rule. They're expendable cannon fodder.

Easiest way to keep Spawn alive are by sating its hunter. Dunno if you have access to Tome of Decay, but the way to reduce its Fatigue is there. It's just difficult to keep them alive as they are, by their own nature, creatures that exist for a very short amount of time.

BYE