Entry Time at Worlds

Need a little help here. I entered the 400 free at Worlds with a time of 5:08. This is a time I did last year at LC Nats. I also went a 5:02 at LC nats the year before in Savannah. If the 400 were being run by age group rather than by time, I would surely put in my 5:02. That way I know pretty much who I would be swiming against. But swimming the 400 by time only means I will be in a heat with people other than my age group (probably) and who knows how much people sand bag. I know I know, swim my own race. Yes, I will, but what are your thoughts on entry time. I'm in the 55-59 age group. Thanks!! Glenn:cool: