My 2 cents, since you asked
At all times you must have the stat. fuel with appropriate reserves, in this case dep2
If you find the trend 'going south' during the flight, and if you anticipate lower EET fuel targets, then you lower your CI accordingly.
Most ETOPs plans have the critical scenario at the end, so this not new.
Some of the build-up may be destination alterates, that may be traded away inflight, but changing the CI accordingly is the most practical.