Are lost gains easy to gain back?

I havent practiced Pe in a long time and I lost half a centimeter in girth. In how much time are lost gains gained back??. This was my girth routine

3 minute warmup with hot water
10 minutes of sadsak slinky lasting 30 seconds each direction
10 minutes of orange bend lasting 30 seconds each direction
15 megasqueezes lasting 15 seconds per repetition
25 dry jelqs lasting 3 seconds each
3 minutes with hot water, then 3 minutes with cold water using a towel