Depends on your nationality, citizenship, resident or non-resident, business model and type of license you choose for your freezone.
A guy with residence in UAE, citizenship French and physical products trading with Freezone in Dubai of course will have better chances to open an account then a guy without residence in UAE, citizenship Pakistan, "consulting" business and Freezone in Ras Al Khaimah.
Normal account opening time is 4-6 weeks. But it depends from case to case and if they don't like your setup in combination︀ with your personal background they will put you in a never ending loop of asking︁ documents.
So make sure that you choose a agent that can you provide the whole︂ setup from A to Z so that you have much higher chances to get a︃ good bank account opened. But guarantee for banking nobody can give you nowadays.