Oncidium & Epicat with new growth - time to move them?

[andrew__]

I recently bought an Oncidium Sharry Baby with the intention of moving it to SH culture and recently discovered that my epicat has very few good roots and needs saving.

The Epicat has one healthy looking root, and a bunch that are sort of dark and mushy. It has maybe 8 backbulbs (shriveled but still with some substance to them), one growth from this past summer (firm, fairly healthy looking) and a new shoot that's just poking its way out of the bark. Going to clean off the dead roots and pot up into SH and place in my terrarium until I have more than 1 root, then move back into brighter light.

The Oncidium is not in bloom but has a healthy root system and new shoot coming up. I can wait on this if spring would be a better time but I don't know 100% how these grow and if now or spring would be better. I'd rather wait on this one though. How big should the shoot be (ideally) when it's re-potted?