Actually you guys are both kinda wrong.
First off I think Bushboy was actually thinking of Bromocriptine, not letrozole, as that compound is 100% useless against progesterone induced gyno, as is nolvadex as well. Anyways, in order to be effected by this gyno you have to be doing upwards of a gram a week, so it isn't something to really worry about.
Moriarty is right about keeping estrogen in check throughout the cycle, as high levels of estrogen have been linked to cancers, and even testicular cell death in rats. Keeping levels of E at physiological levels can only be done by using an AI, of which I prefer letrozole.
As for gyno, once you can 'feel' it, it is too late, cells have already grown that may atrophy once E has dropped, but they will not just dissapeer, they will always be there, and from that point on you will be very sensitive to estrogen in that area.
As for the orrigional question, time off absolutely does not equal time on. That is of course if you are interested in maintaining hpta health.
using a compound like nandrolone, in the decanoate ester, will last 6 to 8 weeks in your body once your last injection has been done. That means your cyle was actually 18 weeks long, not 10 weeks. That my friend is 1/3 of the year. It will then take you at least that time to recover to as close as your full normal self as you can.
Most people however can't wait, and end up jumping on another cycle before that time, to feel 'normal'. It's perfectly understandable, however if you are going to practice this, you might as well stay on indefinitely, as the time that you will consider yourself 'not' on you are still actually 'on'. You might as well save yourself any deppression, libido problems, and dramatic shifts in bodyweight (which I might add are the absolute worst for your health) and just continue on a cycle.
If this isn't your goal, keep your cycle's short. 6 weeks max, and use only short acting gear like Nandrolone phenlypropinate, or tren acetate, if you are wanting to use the more heavier drugs. You could use a medium length (enanthate) ester in your cycle if you are taking testosterone, or primobolan, but besides these two I would really stick to the shorter compounds.
Get a good front and time your ending cold turkey at the six week period
The key really is the less time of the year you are on, the better your hpta health will be.