Good to overlap CDR for ealy game?

Yo. So I main riven, and yes I'm willing to take the flame. Point is though by end game my build will more often then not consist of Ionian boots, Black Cleaver, and Youmuu's Ghostblade. And of course lest we forget the beloved Hydra. Plus other situational items. Point is with Ionian, Black and Youmuus right there thats 40 percent CDR. So with the 5 percent from masteries you get 45%. Thing is I play my riven for the early game a lot of the time and having say 15% to start out with is great. But then by late game I'll have overlapped CDR. So i just need to know whether it better to just start with 5% and not overlap CDR at all and get more out of your ruins. Or to put some CDR in your ruins to for that early game.