I actually cleaned my interior for the first time over the weekend since I bought the car new 3 years ago.
My interior is black so markings tend not to show up as much but the leather did appear somewhat a bit dry and hard, especially on the driver's side.
I had a leather cleaning foam which I used first and then I used the lotion. After using the lotion, I did notice that the leather had a nice supple feel to it which had been missing.
I think I'm going to try and treat the driver and passenger seats a couple more times over the coming months to see whether I can improve it any more.