The longer the lease the better. I suggest that you get at least 1% lease option fee for every year of the option. If they want to extend the option, just charge them additional option money (which they can apply to their down payment)
If a tenant wants to move out before their lease is up, they still owe you the balance of the lease. This protects you and puts you into a strong negotiating position. Any concession you make for them is your decision.
Before you bought that stock, mutual fund or Exchange Traded Fund (ETF) you did your research to be sure that what you were buying would return a good profit over the long haul. You bought it and over time you look at it less and less.
Ask yourself: when you plunked down your hard earned money did you have any idea where you would sell it or where you might exit the trade should the stock go down instead of up? And suppose it has gone up have you made any plans to protect those profits?
It makes me laugh when I read in the press that buy to let is dead. Well of course it is in most areas! But in some areas it is still waiting to boom. These areas I call hotspots. In 2004 alone I bought 50 properties. I bought in Hull, Stoke on Trent and Grimsby. These properties are no longer hotspots, as they are too expensive now. I've experienced 100%+ capital growth in 1 year which is well received but halts my buying sprees.