It might cut into your weekend study time, but are you also getting more done during the week?
I'd say that there is a slight correlation to being older and/or married in law school, but its not a guarantee or anything. First, you're time management is likely to be better; you won't just put stuff off till the weekend when you have plans to spend time with your SO; or perhaps you've worked a full-time+ job for a few years.
Second, you're not as concerned with going out and drinking a few times a week. With an SO at home, or if you're beyond your "party years" it may just not be an interest. Drinking and hangovers really tend to eat into study time.