all my dragons are offered heat for around 12 hours a day, however its very rare that any will spend more than 3-4 hours basking,...some bask for an hour, then go for a dig in the cool end, then resurface fro another bask in the afternoons, some will bask for the first 4 hours, then crash up the cool end.
because theyre all different, i let them choose.
that being said, on weekends, days when i get home early, and when the weathers decent which we havent had much of this year, they sit on windowsills watching the world go by, on heat bags that are around 30C. (nowhere near basking temps)
with good/regular calcium suppliments, good heat, and good UVB, calcium deficiencies shouldnt occur regardless of growth rate.