He does not need rest, like humans do. As long as he can be useful aboard the ship, why should he not continuously carry out his duties?
There was one time, though, when Geordi was able to convince him.
"I'm taking my shore leave on Devala IV next week. You wanna come?"
"Next week I am assisting in the study of the Tibor Nebula."
"They don't need you for that. Come on, it'll be fun!"
"I have no need of a vacation, Geordi."
"Data, humans take vacations. Don't you it's a human experience you're missing out on?"
That alone had not been enough to convince him. But Data also took into account that Geordi seemed to think that his vacation would be more enjoyable if his best friend was there. And so he agreed, and went.
It was strange. Not unpleasantly so, but everything about it was new. Even being out of uniform was strange for Data. And not having to work—or even having the ability to work—was strange.
They spent their days outside—hiking in the wooded mountains, walking by the lake, sitting out on the beach in the sun. They spent dinner on the veranda of the one-room cabin that was rented to them, and lunches were picnics under the shade of a tree. Geordi even convinced Data to try eating a few things, amused and interested to hear what his analysis would be.
And at night, while Geordi slept, Data would sit in front of the open glass doors that led to the veranda, and paint. He had an excellent view of the lake, which sparkled in the light of three separate moons.
A couple of days before their shore leave was over, they decided to go sailing. It was just the two of them on the Devalan sailboat, riding the wind and the waves out onto the expanse of the lake. The weather was favorable.
"Isn't this great, Data?" Geordi said, standing and leaning out with one hand around the mast. "Can't you just feel the wind in your hair?"
Data did not quite understand the sentiment. His artificial nervous system was correctly processing the sensation of air running quickly over his head, of course, but he did not see how that was significant. Geordi laughed.
A while later, after a few minutes spent commenting on the clarity and blueness of the water, Geordi decided that he wanted to go swimming. He lowered the sails, pulled off his shirt, and dove into the water.
Data leaned over the side of the boat to watch him.
After Geordi had been swimming for a while, he asked a question, out of the blue: "Data, can you swim?"
"I do not know," Data answered, honestly. "I have a higher density then that of humans, so I would not be able to float."
"That's too bad…" Geordi reached the vessel and began climbing back up.
Data was still thinking. "However, I believe that I might be able to compensate for my lack of bouyancy with the amount of force I am able to generate with my strokes."
Geordi found a towel, then paused for a moment. "You gonna try it?"
Data thought about it. His normal approach would have involved a few tests and more calculations, but perhaps, just once, he should simply "go for it," as the human expression goes.
"I think I will," he decided, and jumped into the water.
He immediately started to sink, as he had predicted. His attempts to maintain his position in the water were unsuccesful, though he continued to try until he reached the bottom.
"Data?" he heard Geordi call, his auditory processors compensating for the distortion of the sound waves underwater. "Data!"
He was able to gain a few inches off the the lakebed, but it would not be enough to reach the surface. So he looked around for the shortest route to the shore, which was 1 kilometer and 46 meters in a northwestern direction. Geordi must have been able to see his position, because he soon noticed that the boat was following him.
Geordi jumped out of the boat to meet him on the shore. "Data! Are you alright?"
"I am fine, Geordi," Data told him. His systems were functioning within normal parameters. "Though it appears there is some residual water in my servos, which may be difficult to remove."
They spent the rest of the afternoon trying to get most of it out, and Data apologized for being an inconvenience. He did not mean to waste his best friend's vacation time in this manner.
Geordi just laughed.
Later, on their way back to the ship, Geordi told him, "I'm really glad you came, Data."
"I am as well, Geordi," Data replied, sincerely.
He has found himself accessing the memories associated with that trip mulitple times since then.