Hi there and welcome!
If I will be pressed for time the day I plan to smoke I will prep and season the day before. Other than that I don't make it a habit.
So for example: I plan to smoke a brisket overnight Friday night. I don't have time to prep Friday night because I have other commitments. Solution?
Thursday evening I prep the smoker, season the meat, and put covered in the fridge. When Friday evening rolls around and I finally get home I just turn on the smoker and throw the meat in... done!
I don't notice a difference in flavor doing a dry seasoning the day before vs the moment I plan to cook it.
MARINADES, now that is a different story all together. Same with Brines. I do them the correct amount of time always :)