I find the dip strips a great way to test for consistency... then if an issue makes itself known dig deeper with the drip tests...
The dip strips are very quick and are inexpensive when bought in bulk... I suggest you store them away from the aquarium to prevent being damaged by humidity...
I suggest you test your water whenever you do something abnormal...
The newer you are the more often you should check your water... As the more likely you are to overlook something that could impact your water...
When new to a location... regardless of your experience level... I suggest testing your water frequently to get accustom to the water from your new location...
That said... I don't test my water often at all... If I lookedc through my stuff I'm sure I could find an outdated test kit of some kind...