It’s not bad practice to just routinely change them every year. You should test the batteries every month or so. They’ll usually beep to let you know they’re going dead, but it’s better to be safe than sorry.
Smoke detectors have a useful life of about 6 years. While it’s not necessary to change out the unit every year it is the best practice to change out the batteries every year. It’s a good idea to pick a day that is easy to remember (a birthday or anniversary) and change all your smoke detector batteries out. Remember if the smoke detector is beeping it may not be protecting you.
All smoke detectors come equipped with a test button and should be tested at least twice per year. If the smoke detector does not sound when pushing the test button try installing a new battery. If the smoke detector still does not sound once the new battery has been installed it should be replaced. Also if the smoke detector has beed painted or is covered in dirt/grime it should be replaced.