Is there a time limit on owning a property after purchase?

No. You can own a property permanently until you convey the property to someone else.

You can have a right of the ownership of Japanese property. There is no time limit to keeping ownership of the property.
You can also rent an office and a land. However, there is a time limit to the lease which depends on your contract.

When you have permanent ownership of a property your individual name, you are recommended to consider the legal provisions on inheritance.

For more information
Shihoshoshi Lawyer Akiko HORI

How to Buy a property in Japan