It is worth it to use long term because it is dirt cheap and a time tested, proven supplement.
You are correct that it brings water into the muscle and that the effects will cease once you stop using it. However, a hydrated muscle is a good thing, plus since it may also help you lift a bit more (due to more creatine being available for the ATP-CP energy system), you may achieve hypertrophy gains while on creatine.
The hypertrophy gains you achieved (due to myofibrallar and sarcoplasmic increases) are NOT going to simply diminish once you cease using creatine (although you may lose a small amount of mass due to decreased water retention).
Remember, while it may be hard to gain muscle, it is metabolically much easier to maintain provided your training is on point.
Add to the above that creatine is great for brain function and you can't lose.
James 1:16-17 ESV
Do not be deceived, my beloved brothers. Every good gift and every perfect gift is from above, coming down from the Father of lights
With God's help...Mens sana in corpore sano