Is it effective to tweak the last aligner to make final adjustments to the teeth? Will this produce results?

I started wearing my last aligner in September. My teeth weren't completely straight at the end. In the past ten weeks, my treatment has consisted of tweaks to the last aligner. My visits for these adjustments have been spaced at 6 weeks, then 4 weeks. My next appointment is another 6 weeks. Is this a usual approach? I expected that a new impression would be taken and a new set of aligners made. By the time of my next appointment, 4 months will have passed from last aligner being used.  Thank you for any comments. Joe