It all depends.
If you refer to physical form, that shouldn't take long at all. Missy, Verity, and Shannon have been sharing tips and tricks they are doing to stay in physical form throughout this, even to the point of rolling a ball against a door in their house (plenty of padding against the door to prevent damage). That combined with visualizing the arrow/board/target you're wanting to hit should keep you in good physical form.
Mental form is going to be the bigger issue. A lot of that comes into play based on the results of what you left on the lane. adjustments, when to make the ball change, etc., etc. None of that can be done in a house, unless your last name is Doyle. And seeing that that mental form stays sharp due to repetition, it will take longer to get that back than the physical form, as we can work on the physical form even when not on the lanes.
In short, physical form shouldn't take long; mental form will take longer. Not too long, but at least longer than physical form.
BL.