Ability to use Willpower to get a free success on a roll is a huge advantage, making the one who does it frequently extremely strong: he essentially gets +2.5 dice to any dicepool and is exempt from failing a roll. Of course, NPCs should use Willpower when some power calls for it, for example, to resist Presence, but getting autosuccesses this way seems to make encountering relatively weak enemies very dangerous.
The concept of spending Willpower this way is very good for PCs, since it encourages better roleplaying one's Nature to regain Willpower during the session, but no matter how good you roleplay, if you have frequent combat encounters, it seems like NPCs are going to have huge advantage over players because their total overall Willpower pool is going to be extremely high.
Should I call for NPCs to spend Willpower to automatically succeed when rolling against players?