When deciding when to start a bulk, it's important to pay attention to your body's signals. Look for signs that your current bulk is no longer beneficial and has become detrimental. These signs may include excessive fat gain, loss of energy, loss of motivation, and digestive issues. Additionally, if your strength gains start to dwindle despite gaining body weight, it may be an indication that the bulk has lost its benefits.
To be more specific, you can set a body fat percentage goal. For example, if you're currently at 9% body fat, you can decide not to let yourself go above 12% body fat during the bulk. Regularly test your body fat percentage and once you reach your predetermined limit, it's time to reverse direction and enter a mini-cut to drop a percent or two of body fat. After that, you can reverse back into a bulk.
Remember, the best period of bulking is usually at the beginning when you start seeing improvements in size, strength