Units usually understand you may have a business trip or even vacations, etc. If it is planned according and communicated to your supervisor, I dont see it being a problem. You can make up drill weekends if you have. Ill give you an example. Last month I didnt drill because my wife gave birth late December and my chief understood it. Its not set in stone that you must drill every month, but it is highly recommended to do so in order to maintain a "good year" track. Good year is when you satisfactorily complete your drill weekends and the two weeks annual training. It is important to always have good years so because every good year counts for retirement purpose.
In regards to moving around that is a subject that can be a little bit complicated. If you move to another area and there is a CG station/unit there has to be an opening there for you to drill there. Otherwise, you have to continue drilling at your other unit. I know, it sounds weird. Also, the other option is to go into the IRR, Inactive Ready Reserve.