Strictly speaking a plain u2018Rental Agreementu2022 is valid indefinitely and thus will remain valid until it is terminated.A Rental agreement which has a limited or fixed time period is usually known as a u2018Lease Agreementu2022 .There is usually no restriction on how long the time period can be. The stamp duty etc payable for registering the same can vary based on the agreement period, this rate is defined in the local Stamp Act.Usually for very short term leases a Leave and License Agreement may be used. There can be a time limit for such agreement which depends on the prevailing local laws.Please note that even though they are all commonly referred to as rent there are very significant legal differences between Rent , Lease viz and Leave & License agreements. Each is be appropriate for specific purposes and are not interchangeable.Kindly note I am not a lawyer and you should definately consult a local lawyer to get advice appropriate to your situation.