FoC - Just talking from personal experience, it takes me max. 2 weeks or so to get over the blisters (I'm talking until they're fully healed and the skin's back to normal - so you don't need plasters anymore) Any longer than that and I wouldn't even entertain the idea of trying a pair on.
Also, if you're just getting into running, I'd HIGHLY recommend going to get your gait analysed (if you're thinking of upping mileage/getting more serious about running). I learnt this the hard way, I've ran for 5 years and because I'd never been injured, I stupidly didn't bother. Then I got a bad injury and had to take 6-7 weeks off running and use a crutch for a while. It wasn't much fun, and even more annoyingly, it could have been avoided if I'd have had more knowledge on my form/gait.
Good luck!