My very good friend died in very tragic circumstances 4 years ago. Her husband kept the profile, as it was where the vast outpouring of public grief went. He hated it and has now deleted the entire account down to just photos.
I want to delete her off my friends, as it now feels a bit weird, but it also seems a horribly disloyal thing to do.
I think it's time but it will be hard no matter when you do it. I had a similar issue with a cousin who died and it felt disloyal to delete her mobile number. It felt too final for me. But I did it as it was painful seeing her name knowing she'd never text or phone again.
I think it isnt nice to delete the profile or the number immediately, but after a while it is recommended. First because they will always be in the memory of loved ones and you can have photos with them in your personal archive and secondly because it would be weird that people who do not know them and dont know the situation could write comments. The loyalty issue is not affected by the fact you keep the telephone number or if you have them as friend on facebook.
We have that problem right now with a family member who committed suicide last year. Actually I have no idea how to delete the account, and no other family member is closer than us, so nobody else is going to delete it either. Presumably Facebook would - rightly - demand all sorts of proof of identity before deleting, and we constantly have bigger issues to deal with.
What really upset me was getting a mail from his e-mail account months after his death - presumably somebody had hijacked the account, it was some sort of junk advertising sent out to all the addresses in his address book.