It seems like because Hebrew has no similarity to English if it's not used on a fairly regular basis, it would be very easy to forget. Did you find that happening to you when you learned Hebrew?
There were ten of us in the class, and we tried to practice what we learned on a daily basis. About six months after the course, I went to Teheran, Iran, for six weeks. There were some Jewish merchants who sold stuff to tourists and I went there a couple of times to practice, and believe me, it’s a lot different in the real world than it is in a classroom environment. There was a thriving Jewish community until the son of satan, khomeini, took over.