Never get a 45min session. From my expeirience they've always been at the 30-35min range. I've never asked but they'd probably say something like, "What's a minute or two." when it's really fifteen minutes or so. Either do 30min of 1 hour. 45min is a gray timeline. At B&S they say 50 for 45, without offering a 30min fee, so they get that extra $10 that nobody else really charges. I know it's frustrating, but that's the way it goes I guess.
PS This is not only about B&S. This relates to many places who only offer 45min, 35min, etc.
PSS If they really do stay 45min it's a good price...although it's only $10.