You probably shouldn't. If you're anything like me you rarely remember to use them at all, let alone hit them every single time they're up. That said, if you really want to factor them in, add the following to your +healing:

For example, if your trinket gives you +200 healing for 20 seconds with a 60-second cooldown you would use 200 * (20 / (20 + 60)) as your bonus (in this case 50). If you want to factor in your forgetfulness, just increase the cooldown appropriately (set it to a five-minute cooldown if you only remember once every five minutes, for example).

Is there a use for it outside of soloing and certain PvP scenarios? The only PvE healing purpose I've ever used it for is to heal someone slightly while running back through a cleared instance after a wipe. If there's enough interest in it I'd be glad to add it to the charts.

The pseudo-code below is a modified version of the actual formulas used. You may contact me via the Contact Us option in the main menu if you have any questions, or post them to our forums. Please let me know if something doesn't look right or if you discover any bugs.

• Flash of Light:
• Flash of Light Average Heal Amount:
• (($base_heal + $healing_bonus * 1.5/3.5 * ($downrank_penalty_level / 70) + $BoL_bonus * $BoL_percent) * $talent_heal_bonus * $healing_light_bonus * (100 + $total_crit_chance * $crit_value) / 100
• Flash of Light Real Mana Cost:
• $base_mana * (100 - $total_crit_chance * $illumination) / 100 - $mp5 * ($cast_time + $lag_time) / 5
• Flash of Light Health per Second:
• $average_heal_amount / ($cast_time + $lag_time)
• Flash of Light Health per Mana:
• $average_heal_amount / $real_mana_cost
• Flash of Light 1-Minute Chain-Cast Output:
• $spells_per_1min = 60 / ($cast_time + $lag_time)
  if ($spells_per_1min * $real_mana_cost > $max_mana) {
  $spells_per_1min = $max_mana / $real_mana_cost
  $regen_time = $spells_per_1min * ($cast_time + $lag_time)
  $mp_regen = (60 - $regen_time) / 5 * $mp5;
  $spells_per_1min += / ;
  }
  $health_per_1min = $spells_per_1min * $average_heal_amount
• Flash of Light 5-Minute Chain-Cast Output:
• Same as Flash of Light Real Mana Cost, except use 300 instead of 60

• Holy Light:
• Holy Light Average Heal Amount:
• (($base_heal + $healing_bonus * 1.5/3.5 * ($downrank_penalty_level / 70) + $BoL_bonus * $BoL_percent) * $talent_heal_bonus * $healing_light_bonus * (100 + $total_crit_chance * $crit_value) / 100
• Holy Light Real Mana Cost:
• $base_mana * (100 - $total_crit_chance * $illumination) / 100 - $mp5 * ($cast_time - .5 * $lights_grace_percent + $lag_time) / 5
• Holy Light Health per Second:
• $average_heal_amount / ($cast_time - .5 * $lights_grace_percent + $lag_time)
• Holy Light Health per Mana:
• $average_heal_amount / $real_mana_cost
• Holy Light 1-Minute Chain-Cast Output:
• $spells_per_1min = 60 / ($cast_time - .5 * $lights_grace_percent + $lag_time)
  if ($spells_per_1min * $real_mana_cost > $max_mana) {
  $spells_per_1min = $max_mana / $real_mana_cost
  $regen_time = $spells_per_1min * ($fol_cast_time - .5 * $lights_grace_percent + $lag_time)
  $mp_regen = (60 - $regen_time) / 5 * $mp5;
  $spells_per_1min += / ;
  }
  $health_per_1min = $spells_per_1min * $average_heal_amount
• Holy Light 5-Minute Chain-Cast Output:
• Same as Holy Light Real Mana Cost, except use 300 instead of 60