I wouldnt say 100%. It depends on how hard you train and how perfect everything is during your PCT. Diet, rest, supplments and your training program and intensity.
I personally know for a fact that PCT is going to be hard so I always prepare myself mentally when its close and I really push through it hard, perfecting all factors in recovery. This is where 90% of dudes fail to keep their gains.
I have kept up to 70% of gains after a cycle. Goodluck!