A 30-06 is not too bad on a barrel, I would say in excess of 3,000 rounds or more (unless you abuse it by overheating it). I have heard of .308 lasting over 5,000 rounds. Most 30-06 chambered hunting rifles last a lifetime, and are handed down without a barrel replacement.
When the groups start opening up that indicates the barrel is going south, (throat area), and can be set back sometimes. However for a hunting rifle, groups opening up a little is nothing much to worry about unless you are hunting at extreme ranges.
Andrew