Gains can come at any given time and the reasons can some times be elusive. Keeping a journal will help as far as having a history to look back on in hopes to see what created the gains. For me gains were steady in length for me but girth was a different story. Girth came in strange bursts over the years I have trained. In my first year I was only able to gain .5" of girth in comparison to 2.5" in length. My second year when I started to do super-sets and an early version of SlowSquashJelqs I saw girth come on in .25" chunks throughout that year and into the following years. There was no real rhyme or reason, just appeared.