Hello Eric and fellow Mozers,
Yes, I believe you should... probably*. Even though you have invested your time to review all your business listings, Moz local goes a step further. It pushes your listing information out to the main data aggregators. Most businesses and SEOs (myself included) are not able to consistently influence this data for a few reasons, and consistency is key.
Moz Local helps keep the aggregators' data consistent. Without it or your continued time investment, aggregators like Infogroup and Localeze will eventually change your listing information. That bad data will then, in turn, be disseminated to your edited listings.
*Probably?
The effect data aggregators have on your listing varies. I believe this depends on your location and how many times that location's data has changed over time. You might be fairly far removed from these changes if you are well established or a new business in a newly developed area. Still, the cost is so negligible. Just do it and save yourself time.
Why Aggregators Change Our Listing Data
I've not had a unbiased answer to why this happens. The best answer I've heard (in my opinion because I've seen correlations that back it up) is from Vizergy's rep at Yext*. They say, aggregators switch or rollback listing info when they lack information or are presented with strong, conflicting data. Most often, the published data is reverted back to older, more verifiable data. This often winds up being a relatively data phone-book entry.
*Yext and a quick note on bias. I'm not personally bias to Yext or Moz Local. I like what works for my clients' needs. However, Yext is bias to their own product, and it is in their best interest to cast doubt on data aggregators.
Keep it consistent,
CopyChrisSEO and the Vizergy Team