90% DINK or SINK couples by choice in 30s will be feeling purposeless and lonely in 40s.
In 30s, you are young, newly married, a lot to explore about each other, you'll have friends who are either single or newly married, you can have company with similar types of people. But as time passes, things get boring, your friends become parents, their priorities change, they're no more pack the bag and let's travel the world, they are now busy in dropping kids to school and bringing them back home, their travel schedules dependent on their kid's school schedule.
And suddenly you start feeling lonely, purposeless in life, you don't know why you're earning, where to spend and all. Human is a social animal as they say, you can't live in isolation and be happy forever.
Don't fall for instagram DINK couples life, that works only on Instagram and that too for a limited time.