batteries degrade over usage, they are always going to fail you eventually. Batteries are also a non consistent part. You can take 10 laptops of the same company, with the same specs and parts and use them in the exact same manner and get different battery life out of them.
The harder you use a battery the more prone it is to fail. However, my current laptop is a 3 year old Macbook Pro, which I have shut down maybe a dozen of times. I let it sleep and charge it up, but I gotta charge it every day, or every 2-3 days max depending on usage. If you let your battery drain too much it may drain the back up cell, which will in return kill the battery.
So, don't be afraid to sleep your laptop often, but if you aren't going to use it for an extended period of time, turn it off. Like if you don't plan on using it over a weekend, or a vacation, etc. If it must run 24/7 pull out the battery and let it run off the AC power only.