Have you read some of our musing about Capacity vs Utilization?? This might help you understand how I am going frame my answer.
Before the trip, you were building up your work capacity bank account. Making deposits daily with your training plan. By the end you had what you thought was quite a big cash cushion in the bank so you could go on a spending spree (utilization) while on your expedition. Unless you specifically designed this trip to include 7-10 capacity building training blocks your fitness was dropping the whole time you were on that trip. This scenario is high unlikely. Each hard day withdrew enough more from that bank account such that you were mainly resting between hard efforts rather than Jonesing to go training on your ‘off’ days. If some of the efforts were huge then you came home with massive debt that needed to be repaid. You needed first to get rested, during which time you would be losing additional fitness and then you needed many weeks to rebuild some of lost fitness.
After his Nanga Parbat climb in 2005 Steve was pretty exhausted for most of a year.
How do you avoid this? Have your capacity so massive compared to the demands of the trip that you can come home fresher and resume training with out weeks of rest. There is no formula because this balance between your capacity and how much of it you utilize is something only you can decide.