This is so true!
We used to split our stay between Disney and Universal; A week at Disney and 3 days at Universal.
Then, as the kids got older, it went to 5 days at Disney and 5 days at Universal.
This is our fourth year spending all 10 days at Universal! Every year I get so worried thinking, "what am I going to do for 10 days"? "This will probably be my last year". Well, we still look forward to it. It has become a true vacation for me. I get so much downtime at the pool and no more "commando" vacation with FOL. We do rent a cabana for our whole stay and just relax. I know most people look at what they can do with that extra $100. I look at it as a "must have". We go every July when the hotel is sold out for the first week and it is HOT! We spend half our day at the pool and we don't worry about finding a chair or running back and forth to cool off. We tend to go off site now and explore more restaurants too. We visit places recommended in Kelly Monaghan's book that we normally would never have the time to do.
Don't worry about "too much time" spent at Universal - to me, there never seems to be enough time.
Hope this helps.
PDG