Older APIs have been deprecated with full support, but this introduces significant maintenance overhead. SMAPI has matured significantly since version 0.40, and its APIs have converged towards better consistency. Since then 23 SMAPI releases were published with almost full backwards compatibility.
The last major breaking change was in SMAPI 0.40 (April 2016). The SMAPI 2.0 release in October 2017 appears as a small bump.
