Titanium should degrade slower than aluminium, although we already have titanium sheets (reference: Feriolli's yellow book).

Federico has conducted measurements over several years in TT20 (before the TED). Seems a large effect of vacuum conditioning.

Johannes has conducted several tests with BSI in TBIU T10 (without target to avoid back scattering), noting a drop in signal.

Holger conducted an analysis showing foil aging: document