Birth control/ illness control is very effective (but you need to address the what if reality)
If you do not want to get married/have kids it only seems fitting you should date like minded people.
Since I never wanted children or marriage I've lived with a number of women who either were not ready or did no want to commit long term (career path, wanting to settle in another city etc.) .
I lived for 4 years with a commuter GF (roommate with benefits what ever). Monday to Thursday we lived together the weekend she traveled to her upstate home where she had a life. We slipped into an implied monogamy Mon.>Friday AM but we never had rules or a formal declaration beyond 'do not bring them here'' that started early when we were in what we then thought of as a shorrtterm roommate situation and started having casual sex.
I spent other meaningful stretches, including 4,8 and 3years in what we termed a renewable We'll Sing in the Sunshine contract.
read lyric
http://www.lyricsondemand.com/g/galegarnettlyrics/wellsinginthesunshinelyrics.html
If yuou are like minded it can work but if one partner wants the traditional 1.7 kids, 1.2 pets and the quaint picket fence forever life it will not.
In the mid1960s I lived in a pretty much freelove commune where sex was very casual but that was of a special time and place that will never happen again.
The preAIDS world of a guy who ran NYC singles bars was vastly different than 99.99% of the population. I'm not saying the Plato's Reteat lifestyle was mainstream . . . (actually lot tamer that the press played it to be---tables chairs & a freakin' catered buffet FGS!)
Plus a number of years where my GF and I in a tri-nonamous relationship with our live in 'wife' who had an exclusive relationship with one guy and one girl outside our 'marriage". ..but NYC is weird.