When you think about it, the books (saga) start with Triss and Geralt in Kaer Morhen, with mixed feelings for each other and they end with them together, in Kovir, this time with no more doubts.
Speaking of the games, and from the perspective of Geralt and Triss relationship, you can see how each of them deal with a specific obstacle that prevents them from fully being together.
W1:
Deals mainly with Geralt tendency to preparing-the-fields-for-sowing every willing woman he comes across. And they are many. Triss being one among the many. Towards the end, the things between them start to get serious, a child, a ring and some other factors are involved and their relationship gets upgraded to somewhere between friends with benefits/lovers.
W2:
The relationship gains strong foundations, symbols are created, and the "mixed" loyalties lodge issue on Triss side gets resolved.
W3:
Said foundations are shaken and tested as the greatest threat to their relationship reappears, Geralt's lover of yore. Yet again loves prevails, they can't help but be drawn to one another and, when things are about to fall appart, for good this time, they finally express their feeling for each other.
Epilogue: Having overcome all obstacles, from both his and her sides, their relationship gets stronger than ever and they end up their days together in Kovir.
It wasn't short, and it wasn't easy, but then again good things are worth fighting for