I learned this from my sister re: leaving a house empty for any length of time (if that's part of your agenda) - Do something to seal off any drains/traps (sinks, toilets, tubs/showers, etc.) that go to the sewer system. If you don't, when the water held in the drain traps eventually evaporates, your drains become open pipes to the sewer system. Your house will......shall we say......start to 'not smell real good'!!
We've seen people seal off toilet bowls with Saran Wrap and use blue painter's tape over the other drain points.
Bill