Cessna 172 - plan on 40 NM unless it's a terminal VOR. Keep in mind that's a guarantee...you COULD pick it up farther away (75 NM is pushing it though). DME could be received farther away, but again, in your case...figure 40. You might get intermittent numbers between 60-40. You can find the above information in the very first chapter of the AIM.

Lastly - aren't you posting as an ERJ pilot???