Bad? No. You can always hang out, get some food, look in the shops, or read a book.
No,it's good to plan to get there well ahead of time,to allow for unexpected delays along the way.
Depends on the airport and where you're going...
For a long haul from a provincial airport, ie. not Heathrow, I give two hours but if you're travelling at the height of the season and security does take ages to get through and you want to buy things etc then maybe three hours would be preferable. I just can't stand the hanging around in airports.
Ha ha! What's being old got to do with it? You either like airports or you don't.