Interesting comparison, Oz.
I started with Lycett, and thought "Stuff it, I've got Mummy, so I will keep Lycett, and hopefully he's back in by Round 8."
As you suggested, I was sure it was a case of "when" not "if" for Mummy, so I thought I'd roll the dice and hold Lycett as a loophole tool at F8, hoping he was back before Mummy hit that inevitable wall.
The swap of Lycett to Gawn was an easy call for me to make last week, as I was sure he would score well against St Kilda and Longer. If I didn't have Lycett sitting at F8, I wouldn't have gotten Gawn, so in that sense, I was lucky I not only started Lycett, but decided to keep him. I'm probably behind on the deal so far, having $300+k sitting on the bench for so long, but hopefully I will reap the rewards now, and I have decent cover for Goldy or Blicavs, if they go down. Having, and keeping, Lycett has ended up with me having (quite coincidentally!) the top 3* averaging Rucks for the season in my team.
*disclaimer - I don't think they'll end up the top 3 averaging Rucks!