If you decide to do this, though, you are going to get a count for that one IP address only once...period. The client could return the next day and if you don't watch it, you won't register their hit as legitimate.
Counters are eye candy, they really don't mean much at all once you get into their nuts and bolts. As with your case, they can be easily spammed, they rate the hits instantaneously instead of discriminating against legitimate hits (you set the time limit, but a legit hit is normally considered 20-30 minutes between hits by a single client). A hit counter also shows hits for that page, not the site. If it is on your entry page and everyone bookmarks a page three layers down, you never register them on your counter because they never come there anymore.
Again, hit counters are nice for the eye, but for analysis of web traffic, use the server logs.
Jim H.