As mentioned in the thread, leaving what you download there to seed is the best plan. Most torrent clients will show you your per-file d/u ratio and if it's below 1.0 just leave it there until someone else nabs it and improves that ratio. It's also the 'nice thing' to do. 
OP is not wrong in his suggestion in general though, if there is a large file that you actually want, freelech or not, look at how the downloader/seeder ratio looks on the download page. Of course, the large files are mainly for the higher speed connections, seeding at a very slow rate you won't see much improvement with large file-size seeds compared to smaller ones.
Personally I always seed a minimum of 150 files and while a large majority of them lie dormant for days, or in rare cases even weeks, they do come back alive. Sometimes they get a Freeleech and the transfers skyrocket and sometimes they get recycled/repromoted and such.
However, again, sometimes a large pack that you're interested in which is in Freelech can definitely boost your ratio, as seen in the attachment below. 
I should note that this particular file is no longer in FL but people are still interested.
Keep up the seeds if you can, to help the community and yourself.
