"This technology turns every router into a potential means for surveillance," warns Julian Todt from KASTEL. "If you regularly pass by a café that operates a WiFi network, you could be identified there without noticing it and be recognized later -- for example by public authorities or companies."
Later...
Inexpensive or older routers either don’t store history at all or keep it for a short time.
Newer models can store more information for more extended periods.
https://www.thetechwire.com/how-long-does-a-router-store-history/