How long are most of you staying privately routed?

As of late we've had some customers at various different tower sites report some sluggishness in the afternoon. As these reports come in I'm able to run speed tests from tower bases and all have 50+ surplus meg. I believe the customers making these reports have legitimate claims and I know they have absolutely stellar links.

I believe we're running into PPS issues on our core router at prime time. As of now we have 6 Public IP's and all of our customers are behind our router and are privately routed. 

My real question is, how many customers are sustainable in this configuration? We applied to ARIN for a block of public IP's in July of last year and got approved, however we've been on a waiting list ever since and I am beginning to wonder when or even if we will get the addresses. 

I apologize ahead of time if my post is vague or sounds stupid. I'm relatively new to routing in general, and still quite ignorant. I've begun taking over what feels to be an antequated routing configuration. Either that, or we have outgrown the feasibility of a privately routed network.

We are using Private Ips and are running into NAT issues for gaming, this is the major reason we are looking into Statics or Publics. I would imagine going the public route would require ipv6 to be issued to you.