Just wanted to add my two cents. Last year I did PE for only three months (September 2016 - February 2017 resting November and December) and had nice gains (1.5 cm, newbie bonus I think).
It has been almost one year since I stopped. Have not lost a single mm either in length or in girth.
●●Glowsticker●●
START ■ 09/16 BPEL: 16.5 cm, EG: 13.2 cm ■ ■ CURRENT: BPEL: 17.7 cm, EG: 13.5 cm