I've held various posts in both primary and secondary schools, including: primary teacher, primary SENCO, primary assistant head. Then, secondary teacher, secondary head of year, secondary assistant head and now secondary deputy.
I've never worked 13 hour days as routine. Yes, I've done 13 hours when we have parents' evenings, open evenings, school plays etc but have literally NEVER in 22 years worked 13 hours more than two days in a row.
I have had to learn to be superbly organised though. I just don't believe that the people on here saying they work for hours every evening are using their time effectively. There is no chance at all that you'd need to plan and resources every lesson you teach, every year - that's just silly. You build up resources and quick ways to differentiate after your first year and then adapt accordingly.
This year, I've had to deal with a brand new spec as I teach English and I've been graded as 'Outstanding' or the equivalent since I trained so I'm certainly not cutting corners.
Ignore the people who clearly can't multitask/ organise themselves and believe me when I say that teaching is a profession of peaks and troughs. I left school at 3:20pm today and have been in my garden all afternoon. I've managed to do the same at this time of year for ever. If anything, I find it easier now than when I was head of year, which is the busiest role in school.
You'll be fine! 