How often should I use timers?

As an e-commerce merchant, I'm struggling to understand the optimal frequency of using countdown timers in my online store. I want to create a sense of urgency and drive conversions, but I'm worried about overwhelming my customers or making my brand seem too aggressive with constant time-limited offers. How can I strategically use timers without causing offer fatigue or damaging my store's credibility? What's the right balance between creating urgency and maintaining a professional, trustworthy shopping experience?