We will be repatriating to Canada next year, and last summer, we bought a house in Canada while visiting grandma. So, no, I don't think it's crazy to buy a house over the summer while on home leave (though to be fair, other people thought we were a bit nuts). We basically purchased a home two years before moving into it.
We had been browsing real estate listings for two years and following the real estate trends in that city, and there were indications that prices were going up and that the city was poised for rapid growth over the next 10 years, which would potentially drive prices up even further.
We feel we made the right decision, for many of the reasons you outlined in your post. We like the stability of having a landing spot when we return, rather than having to live with grandma in her basement temporarily while finding a place to rent/buy. It was easier for us to qualify with a mortgage as our expat incomes are much higher than our Canadian incomes.
Most importantly, we found something we liked, at a price we could afford, in a location we liked. Houses rarely come up for sale in that neighborhood, so we jumped when one came on the market.
One other consideration we had was whether we had family members nearby who could keep an eye on the house / help take care of the house. My sister lives in the same city, so she moved into our house while we are abroad. She contributes to the expenses of maintaining the house, which is a win-win situation because her contributions are less than what she would be paying in rent for a much smaller place, and we have someone looking after our house.