before making an investment on lenses, do ask yourself what do you want to shoot more.

first of all, prime telephoto and zoom telephoto are 2 different types of lenses all together.

Usually when we talk about telephoto zoom lenses we often calculate the ratio of zoom. like for example the 18-200 that you are looking to purchase right now, 18:200 is 1:11 where if you are at the tip of the lens (200mm) picture quality might deteriorate and compromised sharpness and detail on the side of the picture taken. The middle portion is always ok.

Try getting lower ratio lenses, and you will be a better off with the lens.

ultimate travel lens of course it would be great to have the 18-200mm tammy but try getting the 18-300mm nikon VR if you are a nikon user. Other manufacturer for DSLR, i am not so sure if they have the mentioned lens. Of course with even higher ration lens for the 18-300mm, the mentioned above deterioration still applies.

If you are looking for a wildlife photography, i would suggest you go with prime. you will never go wrong. The 300mm f4 AFS from nikon is a good start, other manufacturer like canon, you should be good with a 400mm f5.6 lens. if budget is not an issue, do consider these longer lenses...

all and all, it falls back to what do you want to shoot with a telephoto lens. if daily usage of kit lens is more than sufficient, i don see why there is a need / urge to change to a super zoom lens...

PS: i am still using 18-105VR for paid wedding shooting / travel / leisure shooting, 500mm f4 for wildlife birding shoot....