No, a former FBI *consultant*, who doesn't understand physics, is telling you something that apparently gives you a charge...but it's not grounded in science.
Suitcase nukes are SMALLER than ordinary nukes.
The smaller the nuke, the shorter the shelf life.
The less shielding that you have, the sooner that your electronics and conventional explosives deteriorate from the radiation.
The less fissionable material that you have, the faster you generally need your atomic trigger isotopes to emit neutrons. The faster you emit neutrons, the shorter your half-life. The shorter your half-life, the less time that you have before the nuke simply fizzles instead of booms. Beryllium trigger isotopes can have as little as a 79 day half-life, for instance.
This is simple physics. Moreover, heavy metals like uranium and plutonium are among the most brittle materials known to man, and the slightest bit of humidity turns them into uranium oxide or plutonium oxide (i.e. worthless rust).
So a "suitcase nuke" from 1991 (the fall of the CCCP) is likely little more than a rusted, shattered, fragmented collection of wiring and explosives today.