If you want to make changes to your voice in a few months, practice as often as possible. Every day or every other day. If you're working to increase your endurance for regular performances, you'll need to increase the length of those sessions. The trick is to build it.
Start with small, regular sessions (little and often) to increase your strength, and as you get stronger, work a little harder each time. Finally, if you know an area where you are weak or unsure, visit our site and find the right vocal training tool to help you. And remember that online personal training is available to help you evaluate or adjust what you are doing. Controlled and consistent vocal exercises will increase the acid in the muscles surrounding the vocal cords, helping those muscles do their job more effectively.