Yeah, you might as well just move right on. Being sixty hours, I'm assuming you're probably done with the league and you're just doing sidequests/PokeDex. There's a lot more updated stuff to do/see in Platinum, so you might as well. Don't hesitate to abuse Diamond (provided you have access to a second DS) to get off to a better/more interesting start in Platinum.
Personally, I bred some Pokemon in Diamond and traded over the eggs, ditching my starter entirely. In the ROM I was using newly-hatched copies of Rotom, Porygon, Manaphy, Castform, and Nincada, but I figured that was way too much and keeping all their levels up was a hassle, so in the retail game I just restarted with Goldeen and Nincada. I realized that you get Porygon for free in Platinum and Rotom can be caught fairly early, so I'll get a better start this way. Manaphy was only there because I had an extra egg lying around.