I-485 inquire, same letter, should I call them again? 8 laoshi?

Refiled I-485 on 11/23/2013, almost 5 months, called USCIS (Lincoln), got this letter again:

Based on your request we researched the status of this case. We actively processing this case. However, we have to perform additional review on the case and this has caused a longer processing time. If you don't receive a decision or other notice of action from us within 6 months of this letter, please call customer service at the number provided below.

I remembered PJ laoshi said, it's canned language, should I call them again every month or just wait? I called USCIS for my previous case two years ago, and got the same letter, then didn't get any information for more than 12 months, after discussed my attorney, I refiled 485 with my current company. It took me almost two years to get here.