You want less than a 10C temperature difference between the yeast going into the wort, and the wort temperature. Which is why most of us get it closer to room temp before pitching. If you're not making a starter, then break the internal pack, get it to proof, and then pitch after it's swelled up some. Depending on the yeast age and temperatures, that could be anywhere from an hour to many hours later. I would typically smack the pack before starting to heat the strike water. Since I make starters for all my beers, though, it's not so much an issue. I just pull the starter from the fridge at about the same time, decant the spent starter wort (leaving a little to make the slurry) and go about brewing. By the time the batch is cooled and in fermenting vessel, the starter has warmed enough to be ready to be pitched in.