I Might Have Killed My 7 Year Old Avocado Tree

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When or how often should you repot an avocado tree planted from seed? I would say 2 times first year, after that 1 time a year, in early spring is a great way to care for it. I realized that you have to keep doing this every year.
My huge indoor 7 year old avocado tree is having some big troubles. The leaves are looking very bad and lifeless. It might be nutrient deficient. Sunburn on the trunk aswell. Can we save it with a repot?