My children are 21,19,16,13. The eldest is at Uni leaving 3 behind!
They have responsibility for their rooms and laundry. If they don't bring their laundry down it doesn't get done. They soon learn when they have no clean underwear (this happened). They need reminding about their rooms but I don't make big deal about it and close the door. They soon tidy up when they can't find their stuff because its hidden. So I have 3 less bedrooms to clean.
Can you afford a cleaner for a couple of hours per week. I don't have one but my friend does and she says they are a god send. Might think about that myself.
One thing I have noticed is the lack of devision of labour between 2 adults. That has a great impact on me and I never realised how much H did. So like you I run from dawn to dusk. I don't manage to get any down time every day but try and do it at least once a week. Even if it is only reading.
I won't say it gets easier as they get older just that your trips change i.e pubs, clubs and concerts.