17.2 hours per week, including 3.6 hours on Saturdays. 18.1 is too much, 16.4 is too little.
Oh sorry, I'm illustrating a point by being passive-aggressive.
It depends entirely on your lifestyle, their lifestyle, and both of your desires. Some people are introverts who like to keep to themselves mostly. Others are extroverts who like to be surrounded by people. These and other factors will affect how much time you spend together.
But presumably this question stemmed from another issue. Did one partner accuse you of spending too much time with the other? Is someone feeling like they want you to spend more time with them?
For what it's worth, I see my husband 3 days out of every 2 weeks. I'd like more time, but he works on the road. I've known people to maintain long term relationships while in graduate school, in which they only saw their spouses for 3 weeks out of the year. I start to feel overwhelmed if I see my girlfriend more than 2-3 days in a week.
Gralson = my husband
Auto = my girlfriend