The best time to repot is in the spring time right as the plant exits dormancy, which is usually around the end of February or the beginning of March. However, you can repot it anytime if you wish. I have repotted them at all different times of the year and I haven’t noticed a significant impact on the plant’s health any time I have repotted. If you are asking how you can tell if the Venus Fly Trap needs to be repotted, well, that’s mostly up to you. Venus Fly Traps do better if they are repotted at least every 2 years. Most growers recommend repotting every spring because the soil that they are in can accumulate impurities and it also turns sour. Giving the Venus Fly Trap fresh media every year helps keep the root system healthy and aerated. Using a deeper container will help the plant grow a strong root system, which in turn leads them to growing larger faster. If you have your plant in a pot that’s less than 4 inches deep and you’d really like to see a boost in its growth, I’d highly recommend repotting it into an 8 inch or 10 inch insulated pot. It will really take off then!