How long does it take for HR approvals on a job offer?

After a long interview process (2 months) with a BB firm for an experienced hire position, I've finally gotten some news (though I'm not sure if I should get excited yet): Two weeks ago, I got a call from HR in response to my follow up. They wanted to gauge my interest and discuss salary expectations as they were "likely extending an offer." I was told that HR would discuss the salary with the hiring manager and get back to me with what they could offer. The next business day, HR called again. I was told the salary that they could offer, we negotiated and came to an agreement on a new one. I was then told that they would work on getting the offer together/ the necessary approvals. I was told that they hoped to get it done in a few days but the process could take some time and that I might hear something the following week (last week).

I havent heard anything since (10 business days later) - should I be concerned?