Is it worth getting the extra feedback when I already have four good scoresheets on the beers? I'd feel a little guilty for wasting the judges' time.
Entering a beer in competition isn't wasting the judges' time, that's why they're there.
But, if you don't have competitive beers, there's two reasons to enter them - to get feedback or to support the club running the contest.
If you're cheap and just want feedback, you don't have to enter the competition at all. Just take a bottle of a beer to your local HB shop or HB club meeting and corner someone you know to be an experienced judge who gives good advice (not necessarily BJCP-ranked). Have them taste your brew and give feedback. Since you're standing right there, they can ask questions about ingredients, process, etc., to further troubleshoot your problems.
If you are a serious competitor, getting feedback from experienced judges before you enter can also help you decide which beers are contenders and which are also-rans, which maximizes your chances of winning.
Of course, if you become a beer judge, or learn to troubleshoot as well as a judge, then you can provide your own feedback. That's one of the reasons why guys like Gordon Strong and Jamil Zainasheff are such heavy hitters in the NHC - they're also great judges.
Finally, if you want further feedback about a beer from a competition, just about every judge has their email address on the judging forms. That's an invitation to send them email and ask for more info. But, if you do send email, be polite and describe the beer - it's unlikely that the judge will remember your beer unless it was really terrible, really good, or really unusual. Also, not all judges respond to email.