when do you switch from sql to nosql tho

ive been working with relational databases for years, and theyve served us well. but lately, with some of our newer projects dealing with massive datasets and flexible schemas, im starting to wonder when the tipping point is. at what point do the benefits of moving to a nosql solution (like document, key-value, or graph) outweigh the operational complexity and the learning curve? anyone have experience with this transition or clear guidelines they follow