I had my wedding dress altered last November about a month before my wedding. The owner was very kind and went throughly over on how I wanted my dress to be altered. I like how there was an option to pay in parts or in full. I wasn't in a rush to have my dress altered, so it took her about two weeks. During my wedding, my dress stayed in tact (I moved a lot!).
If you got your dress from major retailers like David's Bridal or Alfred Angelo's and want to save money when getting your gown altered, I recommend going to Best Alterations instead! The owner will offer a more reasonable deal than the tailors who work at those major retailers.