wheel roll time with no load is cool, but not necessarily equal to better bearings or longer roll time when you are on the board. I’m not a mechanical engineer - and perhaps one can break it down better… but here’s how i understand it.
When a little worn (used bearings) and cleaned/lubed they can roll better than new. The tolerances aren’t as tight (from wear) - especially a lighter oil vs grease - the older bearings will roll longer. the size of your wheels and rotating mass will make a difference in roll time too. And roll time under load (you on the board) may not actually be longer.
And as @PXSS said - wd40 isn’t a lube - it’s a cleaner and leaves behind a tacky residue that then attracts dirt. Go onto silverfish and do a search - the best from their consensus seems to be the lightweight oils like sewing machine oil, bones speed cream, etc.
I still love to see my bearings roll time after a fresh clean and re-lube!