1. Your day no longer finishes at 3pm.
You'll gain at least an hour as teenagers don't need collecting from school. In fact they will actively discourage any parental presence within a few miles of school or anywhere else that they are for that matter.
2. Your liver will get a chance to recover from any possible previous neglect.
Parents of teenagers tend to spend their evenings driving back and forth from various extra-curricula activities. If you multiply the number of activities by the number of teenagers in the house you'll probably find you won't have any free weekday evenings at all. At the weekends when they are out enjoying themselves you'll be on a high level of alert in case you need to go and rescue them because 'the party wasn't very good' or 'the bus didn't come'.
3. You are getting to share space with a uniquely human phenomenon.
No other animals, not even apes, go through a phase of adolescence. Apes skip the strops apparently and move straight on to adulthood. However during human adolescence the shape of the brain physically changes as it is rewired for adulthood. Just keep praying that whoever is doing the electrics is qualified.
4. Teenagers are not the only ones allowed out on their own.
You can legally leave them home alone - for the afternoon that is, not a fortnight in Greece (unless, of course, their brains are fully rewired). So you can trip into town and browse all the shops you want to.
5. You may be discouraged from using such terms as 'lol', 'gtg,' 'fml 'or 'sick' because it just doesn't sound cool coming from you but at least you have a vague understanding of what they mean.
And in case you were wondering sick doesn't mean vomit or anything else derisory it means great! Lol at their linguistics.
6. You are forced to face up to the truth. You won't be allowed to suffer any illusion that forties are fab.
You will know that you are not young and you are not glamorous and therefore you should never embarrass yourself by going out imagining that you are. Mutton dressed as lamb isn't a term they'll understand though as they're too young to have heard of mutton - unlike you.
7. You will have someone to explain how to upload, download, transfer jpegs, and tell you how you're lacking in Rams.
They'll even be able to help you re-programme the television – if they can be bothered. You may have thought such things would never be beyond your capabilities but sadly as technology grows you'll find your brain capacity is shrinking.
8. You will become vaguely up-to-date with fashion.
Obviously not to the extent that you embarrass yourself (see 6) but you'll definitely get that brown corduroy trousers should never be worn, even if you are only gardening.
9. The days of mutilating your feet with sharp pieces of Lego are now just a happy memory.
You may have to negotiate a path across the bedroom floor to get to numerous mouldy plates and cups but at least you can tread with confidence.
10. Interesting chats.
I'm not going to say it happens often. But maybe just occasionally (if you have not been irritating by talking out of turn or asking too many questions) your teenagers may actually sit down and have a conversation with you.
When this does happen it is something to cherish and is certainly more intellectually stimulating than 'I need a poo mummy'.