I have leased for 3 years, on two differnt ponys. Both leases went really well. I was able to use their tack and I get along well with the owners. They were also 1/2 leases but it normally worked out that I could ride more then my 1/2.
It was also nice because when I moved onto the 2nd pony, I could still ride the 1st one - kind of like pay one, and get one for free!!!!!