We have been baking tape reels at 125F for 5-8 hours. We just did about 30-35 in March and transferred them fairly immediately. Only had to redo one (there's one in every crowd). Put them on metal reels at playback speed, not fast-anything, and put an empty reel in between the full ones, for air circulation. Let them cool down for at least the same time period as you bake them.
How did you wind the tapes? The ones that I have seen that needed baking the most wouldn't wind at play speed over anything.