For me with Soul Ascendance it varies, but it's usually around 10 hours only IF I try to get it done in a day and go at it nonstop for the inking, toning, sound effects etc.
I ink traditionally with dip pens so I need to be super careful but everything else is digital so that part of the process is much faster.
I don't know how Mangakas in Japan finish chapters within a week or two, they must work themsevles like slaves!
I tend to take a lot of breaks while I draw so it tends to take me about 2 days because I don't want to burn myself out and make killer mistakes.
Hopefully I can finish inking this today.