I was taking a look at the portfolios of some of best sellers (Yuri Arcurs, Andres Rodriguez, etc) at SS and noticed their newest images don't have the SS supersize.     

I wonder... How small are they sending images to SS now? 

Is it a good idea to only send images as small as possible to SS?

I rarely send full size originals anywhere; especially if the royalty structure isn't geared towards different sized images.  I usually resize for SS down to around 3400-3600 pixels on the long end.  This makes faster upload times (smaller images) and makes the images a bit cleaner if there's a bit of noise or it isn't quite as sharp as it should be.