You forgot about the part where Paul directs the couple to take potions or mutilate themselves so they’ll be sterile…oh wait, PAUL DIDN’T SAY ANY SUCH THING!!!
The key words in that passage are “mutual” and “prayer”. The couple has to agree, and if they can’t, perhaps God is calling them to have another child? (this is assuming both are believers and one is not being just being a selfish jerk), and they should be praying and strengthening their relationship w/ God during this time. “A time” doesn’t mean any specific time, it could mean a few days, the normal time of abstinence while using NFP, or a few weeks while recovering from the birth of a child, or a few months while waiting out a high risk pregnancy, or a few years until menopause.
Creative way of trying to get the bible to justify contraception, though. A for effort.
In Christ,
Ellen