No, you should not have to; the db engine takes care of that itself.
From Books Online:
If the value inserted is larger than the current identity value for the table, SQL Server automatically uses the new inserted value as the current identity value.
So, SQL Server auto-adjusts the identity value up as you add higher-valued rows.
SQL DBA,SQL Server MVP(07, 08, 09) Prosecutor James Blackburn, in closing argument in the Fatal Vision murders trial:
If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them.