What a pain!
I think an extended regression at this age is not uncommon. There can be a number of factors involved - there's a spike in separation anxiety around this time (maybe? best guess), and sometimes there are teeth and other stuff going on, too.
I would also just give up after 10-15 minutes. It's often not worth the stress and effort Though, having said that, 30-45 minutes would count as a pretty quick session for my kids
Good luck!