fucking hate when customers are like this. If you turn up after the official start time then it is 100% your fault if the adverts are shorter than you think and you miss some of the film. And 45 minutes, what an idiot. Most cinemas play around 20 minutes of ads/trailers, sometimes less sometimes more. (at least here) I personally would not risk being later than 10 minutes.
I am sympathetic to customers when we have less ads than usual - 95% of the time it's 20 minutes, so customers get used to that. Sometimes on opening weekend of big movies, we'll only run 10 minutes of ads, and then people turn up a few mins into the film. I do sympathise with them... but at the same time it's their fault and if they get angry then my sympathy will vanish quite quickly...