It sounds as if you have too little non-contact time and are unlikely to get anymore. Whether you realised it or not, you have entered into a tacit agreement with your employer that you will be taking work home with you.
That free laptop was not for fun, it was a bribe, and by taking it you have joined the ranks of suckers collectively known as the teaching profession.
I'd think twice about adjusting your timetable in the way that your colleague has as it may backfire on you. Some lessons don't need planning, but most do. I would not want to go into a lesson with only an idea of what I was doing, whatever the advantage to my social life.
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