After you file

The 60-day guideline isn't set in stone.  It could take less time and, unfortunately, it could possibly take longer. 

Just try to be patient and not worry.  

If you read Understanding Your Letter 4464C, which HelenC12 linked above, it mentions that the IRS is verifying income, expenses and credits, but also that you should consider getting an IRS Identity Protection PIN before filing your tax return.