Yes, Bishop Gerasimos of Abydos of blessed memory cautioned his priests and Holy Cross students, don't ever try to do anything without a service book in your hands; you never know when your memory will lapse.
I'm a layman. Years ago, I memorized all the auditable parts of the Divine Liturgy of St. John Chrysostom in English and much of it in Greek. You will find though, as you get older, you do not learn as quickly as you did when you were young. I've not memorized another service since; haven't even memorized the epistle readings for baptisms, weddings, and funerals, which I've been chanting for 35 years.