Hi to all--

I suppose this is a general maintenance type question, but here goes. 
I've been having trouble with vacuum leaks for the last couple weeks. 
Most recent was the pink vacuum line at its connection to the throttle
body.  As I was pulling into my driveway (fortunately!), it came
disconnected.  The throttle wasn't quite working right after I
reconnected it.  The rubber vacuum line that is used as a connector
looked old and worn, so I replaced it.  Throttle's happy.

Question--As the vehicle is 9-10 years old (has 131K), is it simply time
for these rubber pieces to be old and worn?  Should I go ahead and
replace all of them (I really don't enjoy being stranded on the side of
the road--an event which has occured WAY too often).

If I should replace them, how much is there?  I know both ends of the
white one and the other end of pink.  Air intake boot already replaced
(BAD vacuum leak there).  Where else could it spring a leak?

Thanks for everything!!
Tonya