The only thing between you and blackjack profits once you master counting cards is being able to play in the casino. Casinos don’t like card counters, and when they think you are counting, they will ban you from playing.
You can use many different techniques to avoid getting banned and you should use as many as you can. One way the casinos identify card counters is by watching their bet spread. The higher your bet spread, the more heat you are going to come under. But if you don’t use a big bet spread, it reduces your profits.