I have won a couple of them over the years but it wasn't from doing a lot of entries. When I see an unlimited I just add it to my dailys and bookmark it. I enter it from my dailys and then again when I ago thru my saved bookmarks.
I think they are a waste of time and I rarely enter 'em. That's just my opinion of course.
Not to long age I read a post on another site where an individual had entered a sweep 10's of thousands of times because he really wanted to win the prize. He didn't win
That's the mentality and drive of some folks.
I'm reminded of the Suzy Orman sweep. It was an uinlimited entery cash award for something like $20,000. The site was brought down numerous times due to volume.
Personally, I'm unwiling to sit on the computer 24/7 trying to win one particular sweep. I might consider once per day, but it has to be a fairly valuable prize for me to even consider it.