Those of you berating OP I think are being a bit mean spirited - she didn't say she didn't work at all - she just works less hours - that could be 2 or 30. Even with a SAHP it is not on that the worker gets to come in flop in the chair and say "make us a cuppa, where are my slippers, did you get my washing done and whats for tea?"
Life always has jobs to be done - the SAHP is working as well whatever you think the value of that is - its facilitating enabling the other party to work for a start - without which some of the higher powered jobs couldn't be done.
It is not right that all birthdays and occasions are handed over, all gift buying, seasonal house decorating, DIY and family organisation also gets handed to SAHP. When does the SAHP get a chance for feet up and 5 to themselves.
Teens can be as demanding as other small kids - there is a level of independence and also being able to help (after some meithering) but there is also a level of running them to appts, sports fixtures, events and so on that still requires parental involvement. E,g, my latest is getting some passport photos and buying some clothes before Friday - I pay for clothes and yes she is due some and we are too far out for public transport etc so I get involved.
SO yes often the partner working more hours feels a sense of entitlement regarding those unworked hours the other gets and sometimes takes advantage of that but lets face it houses don't clean themselves in 5 hrs, shopping doesn't get done, admin doesn't get done, children don't get sorted, rooms don't get tidied, decorating and DIY doesn't happen nor does the lawn or washing sort itself out - even those working the long hrs need to do some stuff and be responsible for making it happen without being reminded that it needs to happen.