Entropy is a thing. Keeping a machine running for 10 years without regular maintenance is challenging. 100 years is very hard but within the realm of feasibility. 1000 years might be doable with advanced enough self-repairing technology and access to sufficient fuel. 100,000 years? There's no way any moving part of any kind is going to keep going for that long. maybe if you can figure out a way to eliminate all moving parts of any kind; but even then I suspect random radiation and micrometeorites might erode any ship beyond hope of recovery. Perhaps there's little enough of that in the intergalactic void that intergalaxy travel is possible, but I wouldn't rate it as likely.