It really depends… In preparing for any half marathon race, it's essential to develop your endurance and speed in a way that builds upon your current level and progressively increases it. If you set a realistic goal that is achievable based on your current fitness, you can typically prepare for a half marathon in about 12 to 16 weeks.
A shorter training period of around 8 weeks is also possible if you're already close to your goal or have made significant progress with your training. This might be the case if you've recently completed a running event successfully and want to add a half marathon to your schedule. Alternatively, you may want to make it a bit easier on yourself by setting a target time that you could achieve with relatively little effort.
Longer training durations for half marathon plans can sometimes be useful, especially if you want to take a very cautious approach or if you're setting a goal that seems overly ambitious. However, consistent and regular training is essential, so you can't significantly reduce the "difficulty" of your training simply by extending the duration of your plan. Ambitious goals require ambitious training! Moreover, with longer training periods, motivation can often wane sooner or later.