I'd always go with a gradual fade. Why play by their rules and make things easy for them to implement their hideous shunning rules?
I faded years ago and it makes things easier all round. I quite like the dilemma most of them find themselves in when not knowing how to treat me. It perplexes them also that they have to see me living a fairly good life. They're privvy to stuff about my life that they certainly wouldn't be if they shut down all communication.
Of course, whatever you decide is your choice and your truest of friends will always stick by you regardless. Of that number you'll only ever have a few in life but I've found it's all you need.
Im all for disempowering their stupid rules.