End re-spawning NPC guards?

This is what I hate most about RPG and most RP games....You kill a guard or get the boss down to 1% of their-health and you then die. The boss re-generats to full health. The NPC guard re-spawns after you kill them and you teleport back to get ur way-to-fast weapons detorating from only two npc's that attacked you and you get back and a full compliment of NPC's are all back. I haven't even gotten to the main boss on the Elixar well because of this mechanic that has npc's health or life rejeneration. FYI: I'm a 70yr old man and my reflixes are not up to par for this task.