I used Tribex solo for about a year, cycling on and off as recommended using varing dosages. I think of Tribex as a long term supplement. Think about what it does: it boosts your T levels up, maybe even to high normal depending on where they are to begin with. This doesn’t mean that you’ll blow up like a pro BB, but it does mean you’ll be able to gain muscle easier, feel better, get horny like a 16 year old etc… So over the year I used it solo I was able to make faster-than-average gains than when I wasn’t using it. (And I’ve been doing this long enough to know what to expect of myself.) I still use it and recommend it, but I stack it with other stuff these days.
The original Tribex studies were done with college athletes I think, and most made good gains, 4 to 7 pounds, something like that. IMO, everyone can benefit, but the older guys tend to “feel” it more.