hi and welcome
re power reserve, You are comparing apples with potatoes.....totally different
SA....movement winds the spring which then runs down over 42 hrs through a controlled geartrain
seiko....movement charges a capacitor which releases electrical energy to power a micromotor
its a bit like saying my car runs 300 miles on a tankful but this here solar car just keeps going til its dark!
there are some mechanical watches that run 8 or even 10 days but they are a)expensive b)rare c)have huge springs or even double mainsprings
check out the panerai 8 day or patek 10 day watches.....seriously fabulous but similarly pricey
