To the usual list of reasons for heading to Florida at this time of year, winter-weary northerners can add another: the opportunity to see a wealth of Rembrandts and other jewels of Dutch Golden Age painting. The occasion is “Art and Life in Rembrandt’s Time: Masterpieces From the Leiden Collection” at the Norton Museum of Art, through March 29. It’s an unparalleled opportunity to do a deep dive into one of the most dazzling epochs in the history of art and, at just over 70 paintings, one that is perfectly scaled.