The most recent AA retirement schedule for these aircraft is apparently 6 in 2019, 13 in 2020, and 5 in 2021. Given that they're only committing to 20, this means it's most likely 6, 9, and 5, which is actually a schedule that's completely doable if the demand is there. Smart to tie these up, for fleet consistency and the potential for a resale if necessary. There will be plenty of similar aircraft coming off of other carriers in the same time period, so it's not like they're cornering the market, but they will have a largely consistent base of feedstock to convert. Apparently, the onesie-twosie nature of the 767 fleet at GTI adds some additional challenges for the crews and maintainers.