There can be uses for multiple files ( i.e. data seperation, reports, completely different modules ) and there is no universal answer to when to do it. It is on a case by case basis.
However in your case from what you have posted, I would stick to putting it in the same file.
Perfect !! That seems to be workig out for the best. Especially since 90% of the data on a work order is already in the projects file. Thanlk youi very much