dev journal 18 covered this. it said that running a town would take around 4-6 hours a week, a city would be 6-8 hours a week. We don't really know what those duties are but i would assume that being absent for a couple weeks at a time would be problem. you would have to give other people the authority to act as mayor and make decisions for you while your gone. Letting someone else send taxes to the count wont be a problem but there might be features that only you the mayor have access to. I would just assume that it may cause some kind of problem since major things might happen to the town without you knowing about it.