Automated regression testing is required if you're looking to incorporate Agile and DevOps practices into your development lifecycle. But if you create too many test scripts or have extremely complex test code, you might be causing yourself significant long-term maintenance challenges.
Ultimately, it's about prioritizing what should or needs to be automated. There's no magic number of 'just enough' or 'too many' test scripts. Rather, your teams needs to take several variables into consideration, including ROI and speed.