Bale has been instrumental in Tottenham Hotspur's progress in the Premier League and Europa League, but Wenger believes that it is only a matter of time before the goals begin to dry up.
The Gunners boss told reporters: "He has good pace, a good shot and his pace is an advantage to use with his shot.
"And at the moment he has a good conversion rate between the chances he creates and the goals he scores. But that goes in cycles. No [he won't play like this forever].
"To maintain that conversion rate, which I think is the best in Europe, is very, very difficult."
Wenger takes his Arsenal side to White Hart Lane on Sunday for the North London derby.