...the fact my T said that, in a way, he will always be with me and I will always be with him - it helped that he said both parts of that.

I think this is crucial. Hopefully, by the time you leave therapy, you will have internalized your T to the point that he will always be with you, yet you will feel separate from him. This occurs whether you stay in touch or not, and it greatly mitigates any continued sense of loss. Of course there will be a period of grief at the time of stopping therapy, regardless of how well-planned the ending is, and independent of whatever connection comes after that time. But such grief is transitory and appropriate.

My former T is over 80. Although I don't know the details, nor whether it is his health or that of his wife, I know something serious has happened because he hasn't responded, and that is very unlike him. It saddens me that he's facing some sort of challenge, but while I am concerned, I also feel calm because whatever happens, we are connected. That will never change.