I love fics where the two of them grow old together. I really do. It's one of the few times I'll tolerate sap. I can just see them, with Snape still being grumpy and snarky, and Lupin, who sits by the fire and reads and drinks tea, loving him just the same, and just shakes his head a bit and smiles indulgently.

It does get to me sometimes, because I'll never have someone to grow old together with.