Yup... I also recommend just keep them clean with regular soap and water.
BUT... I don't recommend using any of the "Protectants" on the market. Most of them are just soluble oils... and they actually harm the vinyl.
If you want them to look good for a long time... when you are done with the boat... get it covered, or in the garage. UV and weather is what makes the seats brittle, hard, and ugly.