This launch was to 500km, and the Doves are around 150kg/m^2 (4.5kg / 0.03m^2). This puts their lifetime at around 5 years according to that linked plot.
For reference, Planet's earlier launches were to the ISS (400km) and lasted less than a year, which your plot agrees with.
For reference, Planet's earlier launches were to the ISS (400km) and lasted less than a year, which your plot agrees with.