We know from what has happened with other people on the forum that INZ take applications seriously with 2 - 3 months' worth of evidence of living together. See old threads for examples and discussion.
https://www.google.co.uk/search?sour...k1.Zc7AdOdCVVE
However, this is not all that is necessary. They will normally require more evidence of continued living together covering all the time of processing of the application before a visa is granted. This is making sure that they don't issue a visa to someone whose relationship has broken down in the meantime. What you say in your post sounds as though you are thinking you may be able to move out and live nearer your work again when you have gathered *enough* evidence, but it doesn't work that way. INZ regard a partnership as people living together on a settled basis, and continuing to do so.