It is indeed permanent and is certainly not a way station on the road to marriage. Becoming a nun is a serious commitment and made with the intention of it being for life.
I disagree. If that’s what you want, that’s fine.
However, if you want to be married, but your time is not yet, it’s better to take a temporary vow to do the most good until you are ready.
The Jews had the Nazarenes. Being a Nazarene was a one year commitment, where you kept the Torah perfectly. However, God did not expect that to be permanent.