Let's say I am predicting weight from height (cm) and age (years). Then I decided to convert height into meters and age into months. The interpretation of the coefficients out of the regression might be not that straightforward (I will need to think in meters and months) but I will still get my accurate regression, won't I?

I also thought that the by converting the age into months might be bad for the prediction, as people's (grown-ups) weight do not change drastically within the months, it might change drastically within the years. So, I will get high variance and I might overfit, is that correct?