If not in Business/First then 20-25 minutes each way. IIRC, you arrive 1 third the way down one arm of the satellite's cross, head to the hub, go up on level and along to the lounge. Going back from the lounge you need to return to the hub go down a level and proceed the the verry end of the West arm for the bus.

If in business, they use an area between the currently train free platforms near the center of the hub.