Does anyone know if there is a "standard" cut off age for men and/or women who desire to enter monasteries as novices?
Is there such a thing?
No but this varies from one monastic community to another. Some may require that you to have been in a monastic setting before age 20 while other welcome those who are very advanced in age.
Also, does anyone know if there is a "typical" duration for remaining a novice?
There is no set period however each monastic community may have their rules.
Do all novices receive a monastic tonsure upon completion of their time?
There are many who never receive any tonsure, they may just be given the blessing to wear a cassock and skufi. Often the first tonsure is the only tonsure a monk may receive, that is the tonsure of the Rassaphore. This first tonsure is a setting aside but it does not require a monastic vow. Most people you will see in a monastery are actually Rassaphores and not Stavrophore, which requires a monastic vow.