It's simple. It's a definite maybe! If the system gradually got warmer over time, chances are it's a very small leak. (9 out of 10 times it's just an o-ring leaking), and as Mike N said, you can just give it a boost every year, especially if it's a car you don't want to sink too much money into.
I would just say don't use the refrigerant that has the self
sealing capability. I've never used it, but if it's anything like fix-a-flat, that stuff will get into every crevice of the system.
If it's a bigger leak, you may have just spent 60.00 or so needlessly. Also, if all the freon has escaped your system, air is in your system that needs to be evacuated prior to charging.
That's also assuming that other causes aren't responsible such a blend door partially stuck toward the hot position.
So my question stands.....are you a gamblin' man?.