congrats to your son and just to reinforce what others above have said - don't blink because next you know it he will be married and have kids
My 23 year old eldest son and his new wife (well married 2 months ago) have just moved interstate - and to the state that means crossing water to get to it - can't just drive down and say hello.
The time just flies by - I remember so clearly watching him born, growing up, going to first day of school, last day of school, TAFE and then a job - all seems so quick now!
PS as for textbook bills - my youngest started uni this year - combined maths and science degree - came home first week with a request for $500 worth of textbooks - now he's changing courses and half of them will be no good to him!