Sample of magnetic WDs within a distance of 100 pc and in the range of mass 0.45–1.05 M _⊙, extracted from the Montreal White Dwarf Database and the 20 pc volume-limited sample of S. Bagnulo & J. D. Landstreet (2021, 2022). We show two lines that represent the expected age for the onset of crystallization of different WD masses for the cooling models from E. B. Bauer (2023) described in Section 2.1 (solid magenta line), and for cooling models from D. Blatman & S. Ginzburg (2024) with oxygen-enriched cores obtained by increasing the ¹²C(α, γ)¹⁶O reaction rate during the stellar evolution (dashed magenta line, see text for more details).