It depends. Generally speaking, you should aim to use your rewards from travel credit cards for travel-related purchases – like flights or hotel rooms. However, everyone has a different version of what “value” looks like here. Some travelers are perfectly content redeeming 25,000 miles for a $250 economy flight. Others would rather save up and use 100,000 miles for a $5,000 business-class ticket. The important thing is to avoid redemptions like gift cards or merchandise, since those typically offer poor value for your points and miles.
Ultimately, it’s up to you to determine whether you want to keep cash in your pocket by using rewards for a particular purchase instead.