For windows I have many of the SmartThings Sensors and the battery life is about 6mo for me. I think it has to do with the constant temperature readings (which are fairly useless mounted to a window) but thats pretty terrible, IMO. I would not purchase for primary use as contact sensors again.
I also just found these beauties but they are expensive and I am not sure if they have been tested with SmartThings yet: http://a.co/2hOvL9v
Finally, for doors, if you are willing to drill into doors and door frames I would recommend these: http://a.co/dNCNIzU
These work very well, have decent battery life (I am over a year now on a very frequently used door), and best of all you forget they are even there.
Along with GoControl sensors, these are similar but uses the newer Z-Wave plus protocols. If you don’t mind the larger size, they are quite reliable and the battery lasts a long time (I would say more than a year depending on traffic).
They often go on sale for under $20
For the price and performance I’d go with the Lowes Iris sensors. I have tons of them. Super reliable, fast reporting, small form factor, and they always work. Now saying all that, no device is perfect, and you also have to factor in ST platform issues.