Yeah, it can be hard not to roll my eyes and groan when they start making comments like that.  I think my all time "favorite" was when we were discussing a comet that only comes through every 100 years or so (this was a few years back) and I said to my husband "We better not miss it, it's not like we'll be around to see it next time." And my sister kind of smirked and said "I will be."  I managed to contain myself, lol, but it wasn't easy!  

"The best time to plant a tree was 20 years ago; the second best time is now"
-old Chinese proverb