You'll typically get all of the oak from cubes prior to reaching the first three month rack time. Just taste along the way and rack off of them if the oak gets where you want it. If not, just let em soak til you are ready to rack.
If the oak doesn't get there, add some new cubes to your target carboy and rack onto them for another three month sit with tasting along the way. That's one of the nice advantages of bulk aging, plenty of time to customize your wine just the way you want it.
Good call. Thanks. I've been away for a few days. Think I'll go down and visit with my wine.