This may help you to understand the application as it would apply to TRT. As for performance enhancement, it would be hard to off cycle because of the extended half-life. The half-life is thought to be between 16-20 days, however Nebido claims it to be 53 days.

These highlights do not include all the information needed to use AVEED(R) safely and effectively. See full prescribing information for AVEED(R).AVEED(R) (testosterone undecanoate) injection, for intramuscular use CIIIInitial U.S. Approval: 1953
http://aveedusa.com/testosterone-lev...ical-data.aspx

Nebido's half life at least is much longer. But notice the considerable variability:

Nebido 1mg/4ml, solution for injection - Summary of Product Characteristics (SPC) - (eMC)

" Following intramuscular administration of this depot formulation the release rate is characterised by a half life of 90±40 days."

From what I am reading it has a lot to do with the suspension. For example, check out this paper:

Testosterone depot injection in male hypogonadism: a critical appraisal

Here it is given as 70+-21 days:

"In a following study (Nieschlag et al 1999) 13 hypogonadal men received 4 intramuscular injections of TU at 6-week intervals. T serum levels were never found to lie below the lower limit of normal, and only briefly after the 3rd and 4th injection were T serum levels above the upper limit of normal (Figure 1) while values peak and trough levels increased over the 24-week observation period. Serum estradiol and DHT followed the same pattern, not exceeding the normal limits. In order to better establish (von Eckardstein and Nieschlag 2002) suitable injection intervals for TU, 7 hypogonadal men received injections at gradually increasing intervals between the 5th and 10th injection (starting with 6-weeks injection interval) and from then on every 12-weeks. Steady state kinetics were assessed after the 13th injection. Cmax was 32.0 ± 11.7 nmol/L and half-life was 70.2 ± 21.1 days."

So, with that being said, the forecasted half-life of any drug is typically a rule of thumb. Another words, it depends greatly on the person, the way they metabolize the chemical, their health, etc. A crude way to determine the half-life for you, you would have to take it, do blood work, record your levels, and take blood work periodically until the testosterone levels in your system half dropped by 50%. I know this probably just adds more confusion to what you already know, so to simplify, try taking it every three weeks and check your blood work periodically. This should work for TRT if your hypothalamic–pituitary–gonadal axis (HPG axis) isn't working correctly. If you can make your own testosterone, I would be very careful not to destroy that function with such a potentially long ester.

CJC4ME