But it does not mean they face an easier task getting to the Grand Final at BT Murrayfield, however, as an in-form Ulster are their opponents.
Indeed, Ulster beat Leinster at the Kingspan Stadium 30-6 last week and then put 46 points on Ospreys to confirm fourth place on Saturday.
And Cullen admits his team must use a vociferous home support to their advantage in the semi-final.
"We're pleased to finish where we have, but it doesn't actually count unless you maximise the advantage you
have," he said.
"It's fantastic for our own fans and the people who have stood by the team all year, that they get to watch us in the semi-final this year in the RDS.
"We'll regroup now and there's the awards dinner tonight and we can pay tribute to certain players who will be moving on.
"Then we can get ready for a huge game in the semi-final. Ulster are hitting some really good form so it will be a really big challenge."
There were eight different try-scorers in total against Treviso, including a double for Richardt Strauss and a score for man-of-the-match Isa Nacewa.
"We started pretty well," Cullen added. "We showed some good intent even though the ball was quiet greasy.
"We created a couple of good chances off a couple of those drives it was quiet pleasing to be watching it."
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