Good question macrossman.
The models of the VF-25 in the model magazines are pro-built all painted, detailed and weathered.
When I built my VF-25 kit without painting but only panel lining, gundam marker and snap together it took about 9 hours or so to build.
I would guess that the ones that are fully painted, lined, weathered, and detailed would take much much more time, maybe 20 or 30 hours?