On second thought, the 2 years time frame my orthodontist gave me was probably both pre and post-op. Puting implants would probably shorten the time of the treatment, but I would also have to wear braces for some time to prepare my bite for surgery. Also, I think it would cost significantly more since I don't have much bone at the extraction sites and would need bone grafts. If aesthetically it doesn't make a huge difference not to have three second pre-molars as long as the space is well filled by the molars, I think it's worth the time on braces to save a few thousand I would spend on implants.