I have learned that a 5″x7″ or 6″x8″ landscape oil painting should not take more than 1-2hours.  If it does, then the artist is unsure and noodling and I have to constantly remind myself of that and to think what I am not sure about and to solve the problem in the head before proceeding.  This 6″x8″, painting was done in 1.5 hours.