IMO, all cats need to have their mouths and teeth examined at each exam - annual for young cats, at least semi-annually for the more 'mature' cats. Just like people, some cats will tend to develop tartar, etc., and need cleaning, more than other cats. My girl seems to go a couple of years between cleanings, my boy needs one every other year, so far - basically eating the same food. My boy needed his teeth cleaned at four - a year after I adopted him. My girl - she was six before she needed cleaning.
Also, maybe ask the vet for advice on how to brush your cats' teeth - that will help dental health as well. Or search the internet for vet school sites, such as Cornell, that usually have videos on how to attempt to brush a cat's teeth. It's not always possible, especially with a mature cat (I know!) but it might be worth checking. There is prescription dental food - there's one Hills version that my vet gave me to try as a treat, but mine just didn't care for it.
Dental health is really important, just like with people - but, sadly, cats aren't very good patients in the dental chair, so you have to knock them out - right there the costs go wildly up.