It's a subject that really confused Luke once he and Lorelai found their way back to each other. This is the first time he's ever been in a third-time relationship, after all.
In many ways, it reminds him of the space-time continuum: it's best not to think about it too much.
So, he decides that he'll play it safe. A man can't go wrong commemorating special dates and giving a woman, especially one like Lorelai, gifts. He's still embarrassed by what happened at the Vineyard, but the light in her eyes as he gave her the necklace at Rory's party went a long way to making things right.
But when he did take the time to think about it, it was almost like they were starting with a clean slate. Rory had discretely let him know that Lorelai had disposed of every item that reminded her of him after the ultimatum. He'd been crestfallen, but oddly enough, felt somewhat better when Rory told him that in the past, Lorelai had merely kept such items boxed up. But with him, she'd been so devastated that she'd literally wiped all traces of him from her life.
Devastated, right...a fine way to show me, he thought, by marrying someone else. Luke quickly shook his head. If this third time was going to work, he'd have to man it up and truly forgive her. And himself.
But other than the occasional lapse, the third time was not so bad. So, he thought, this is what they meant by "it's just like riding a bike." This whole re-acquainting business wasn't as bad as he'd thought it would be.
Lorelai had told him that she wanted to start their relationship off "right". Trouble was, Luke had no idea what "right" was. She said she wanted it to be with him, of course, but beyond that, they were "just friends". What the hell was that supposed to mean? But they plunged right in. Doing the "relationship thing" was a lot of work, but since they'd been friends once before, it felt familiar.
And they talked and talked about their relationship. Post-ultimatum. Post-diner-destruction. Post-her-sleeping-with-'him'. Post-marriage-to-'him'. Post-divorce-from-'him'. Post-car-buying. Post-Rory's-off-after-graduation. So far, being "just friends" meant that this third-time around relationship was a whole lot of talking, with a generous helping of hugs and kisses.
Yet somehow, for the moment, it felt right to Luke, though he longed for much much more. Lorelai was, as always, a perpetual talker and he, well not. Funny thing was, during the time he was adjusting to his newfound daughter, she didn't really talk to him all that much. And hence their problems. Luke never imagined that Lorelai would be the type to clam up when she really should be giving someone, namely him, a good ass-kicking, but she sure fooled him.
But they'd gone through all the stuff they went through, and Rory graduated and Luke made the tent for the rainy party, and Lorelai kissed him at the same time that he kissed her. And she came to him after Rory'd been safely delivered into the hands of the Transportation Security Administration. And he came to her the first time there were problems with April at camp.
Talk. Talk. Talk. Luke and Lorelai. All talk, and well, no action.
It wasn't until a little more than a week after Rory's Bon Voyage party that they really started it all up again, the whole 'relationship' enchilada.