I agree, I'm forever away from my tank being full/mature with nothing left to do but I do wonder when that time comes, if it does, what will I do then? I suspect that's why many keep upgrading/changing setups to some extent, to avoid the boredom of their achievement.
I have a canopy on my tank for the first time ever with this setup and I have to say, getting a top down view is nigh to impossible which is a real bummer. I think in an ideal world I'd have my display with a mature/full blown reef and then have a frag/grow out tank with some duplicates of sps in the display along with some others, but we'll see if I ever get there. On the other hand, I feel it's almost wasteful to keep sps colonies in a growout tank only...but I'm only 50/50 on that sentiment. Which means the other 50% thinks it's a great idea.

I'd like to upgrade my current 25g frag tank to something larger and shallow down the road to accomodate those growout/overflow sps. Always got to have a plan/change in mind, right?
Are your growout/frag tanks a different system or plumbed all into the display? I'm sure you covered this somewhere already that I missed...