Entering Occupied Unit to Show Prospective Tenant

[John C.]

My tenant has provided the required 60-day notice to vacate the rental unit. According to the lease agreement "Tenant shall not UNREASONABLY without consent to Landlord to enter the premise to exhibit the unit to prospective tenants."  I would like to begin showing the unit at the start of the 60 days, but the tenant feels that is excessive and would prefer 30-45 days.  I would think since 60 days was the required to inform the Landlord, that would be "reasonable." However, since there is no specific number associated with what is "unreasonable," what choices to I have if I live in Virginia?