Why should you HAVE to have those feelings. I hate to tell you this, but I love my H dearly but the "thought" of those things doesn't give me those emotions.
The "thought" of my H dying doesn't create total despair in me....the reality of it would though.
I understand what you are saying....but I'm wondering if you aren't projecting what you think you should be feeling, what you think should be normal. Deal with your R as it is. You guys have been together awhile now, you aren't in that "honeymoon" phase where you would be likely to have those emotions at thoughts like that.
You guys know the other is there for you...so that "longing" is very likely to subside a great deal, because you have the comfort of knowing...he'll be there KWIM?