phxwitcher: So when do they actually do something? Last action was a tease at the beginning of the Prologue. I'm at Flotsam right now getting ready to get the herb for the antidote I need to face the Old Man.
Depending on your choices, you can actually not choose to romance (or have sex) with Triss at all. In fact, you can be downright mean about it by the end of the game. :p That said, she's your only "long term" (and I use that in the loosest sense of the words) romance option, so from a roleplaying standpoint, keeping her at arm's length could be seen as Geralt's recovering his memories concerning Yennefer.
Anyways, to better answer your question, sex, or no sex, with Triss is dependent on the Rose of Rememberance quest (in my tireless attempt to bed Sile, I actually tried a game where I didn't sleep with Triss in case that was some hidden flag for the other sorceress to finally decide to succumb to Geralt's charms). When you do that quest is dependent on when you visited Loredo. If you visited him immediately, then you could have done it very soon into the Act. Or, you can wait till you've done everything else, in which case you might not face the choice until the very end of the Act.