Is there a level at some point when color changes/dips are not even an option anymore?

I, by some miracle, am on level 140. In those 140 levels, I think I've had ONE dip, and it was somewhere in Tier 3, I think (maybe early Tier 4?). I keep coming back every day, hoping for a dip, but not a single one in the last 100+ levels. Am I really just THAT unlucky, or is something up? The prizes for this top tier have been nothing but junk and small amounts of TU gain/loss. Not worth it. at. all. I planned to keep it up as long as possible, just to see if I ever get a dip, but I'm having major abdominal surgery in 3 days, and I'll be hospitalized for at least 3 days, so I'm sure between being unconscious and in severe pain, I'll end up missing a day or two (don't get me started on why we need lesser "punishments" for missing a day at the springs.../fumes.). But the way this is going, it really won't matter if I miss a day or not. In fact, maybe I'm better off starting all over just to get a dip or two in the lower tiers...