How persistent are your gains?

I am curious as to how well gains seem to persist through breaks for other members.

Try to include:
What gains you have experienced.
How long you feel the effects of a standard routine.
Changes/expectations during a typical break.
Changes/what seemed permanent after a vacation from PE.
Setbacks you may have experienced.
Any exercises that seemed to maintain gains without a full routine.
Impressions or stats are both interesting BTW.

My current exercise is short and sweet, but can be on the more intense end if not careful. The nice part is, I feel engorged for a day or so after, but my focus is on sustainability. I know new methods can be exciting, but can easily be taken too far, so I’m looking for a framework that could be used for comparison. I should mention that to date have not kept a log of my measurements, and intend to start, but lost 125 pounds in the last year of so. That alone caused my external length to go from 5.5” to 8” BPEL, so I can confirm the 1” per 50 pounds bit. For reference, my girth is right around 5.5” mark. The situation is great, but not for keeping accurate records of real gains. My goal is does not have a number so much as a feel, but I’ll take gains either way.