is there any plan to allow graphics to the game? Like a team helmet or player faces?
You can currently upload your own team graphic banner in the custom leagues, which is one of the premium features. I toyed around with player faces and that's something I'd like to do eventually, but it's something that's significantly down the priority list.
So your purchased credits will never go down unless you try and join multiple leagues in one day.
I think that's a better way of phrasing it unless I got the actual concept wrong.
Yes - your purchased credits will never go down unless you join or renew more than one team in a day, or use your credits to customize your team or players.