Further Discussion on Stun Grenades

[EskrimadorNC]

This recent thread on Flashbangs/Stun Grenades has gotten me thinking about the rules for said devices, specifically this part:

Originally Posted by GURPS - High Tech

A Vision- and Hearing-Based affliction that affects a 10-yard radius. The Protected Hearing and Protected Vision advantages (or equivalent; e.g., hearing protection and dark goggles) each give +5 to the HT roll. Failure to resist means you’re stunned; roll against HT-5 to recover each turn. Also creates smoke in the area of effect.

HT -5 is pretty steep, especially since it's a static roll you have to make every turn (until you succeed).

For a HT10 NPC, that's what...a 5% chance to succeed? In my personal RL experience, normal folks usually recover from the effects of Flashbangs sometime around the 6 second mark, give or take.

When PCs have used them in action games, rarely do the NPCs ever pass the HT -5 roll, and the PCs end up being able to act with impunity for way longer than they should.

Has anyone out there had the same experience? Do any of you GMs have special house rules for stun grenades? Do your players ever even employ them?