I'd say this a little complex because it depends on how you see the game but ultimately yorick is the kind of champion you're looking to scale out of lane into an unmatchable sidelane. If you cant run down the enemy under tower or hit the tower regardless of their damage i'd say its time to group. But you always need to be pushing sides no matter what. Its kind of a balance between you understanding when you can walk up to the side and when you cant and also understanding when you're that much stronger than the enemy toplaner so that you can hit tower freely.
#How do I know to split push or team fight as a yorick player?
topaz dew
Most matchups yorick will be able to run them down after a certain amount of items especially with the current strength of hullbreaker and it being the most gold efficient item in the game. But thats completely dependent on you and your ability to leave lane even or ahead.