In general, ME benefits tend to stick around for the same amount of time that you’ve been training it. But typically we don’t go too far past 12 weeks, so that rule of thumb may break down over longer timelines.
Another general rule of thumb is that a load of 50-75% of a routine should be sufficient for maintenance.
But peak gains never stick around. They come and go. Peaking happens when a bunch of trained systems combine to create a sum that is greater than the parts. But the peak is always fleeting, and overtraining will result if you try and keep it around.
After your event, start the process over again for the next event. Each subsequent macrocycle will benefit from the previous cycle’s training and the general average should rise.