1-For a 12month lease: you will want your lease expiration date to be on a spring/summer to spring/summer schedule so that when and if the tenant submits an intent to vacate notice, you will have acccess to the biggest pool of potential tenants. That means that if the lease expires in Sept-May, you may want to reconsider a shorter lease or more than year and a half lease, depending on the rental income at that point.
2-When not to consider the 12-month cycle-If you are on the "ultimate lease cycle" than question whether or not the rent is high enough. How heavy would your turnover expenses weigh vs. maintaining the same client? Do not forget to consider you optimum rental income potential. Also,...what if you would be able to save enough money for a very good tenant to stick around for another 6-8 month for the same rate? It can be considered a savings fund for the time being where you are holding some of your revenue to put back into the house. A good example of a shorter lease working towards your goals.