I've got a Norwegian Forest Cat who is 11-12 years old. She gets a couple of mats twice-yearly, usually on a hip or near the tail. I either use a mat splitter or cut them off. She's not fond of it, but that's how we do it.
I've recently started using a Grooma Groom on both her and my foster rabbit. Roomba is a Lionhead/Angora mix, so there's plenty of fur to groom. The Grooma Groom brush is great for removing the dead undercoat and keeping both animals looking good.
When I used to volunteer at my former local shelter, we got 26 Ragdolls and 1 Maine Coon in from a cat hoarder. The Maine Coon was such a mess that we had him shaved down to a Lion cut. It was kinder than trying to use more manual means of dealing with the mats.