I have recently returned from an 8-week visit to the USA.
When I did the same trip last year I took some starter with me and used it while I was over there (it seemed perfectly happy on a diet of King Arthur bread flour). That was all a bit of a fiddle so this year I decided to dry my starter and restore it when I returned home. I used the method recommended by Eric Rusch:
I took a little of my starter whilst it was at its most active and, using a rubber spatula, smeared some on a piece of baking parchment, keeping the coating as thin as possible. I put this in my warming cabinet at 30°C until it was bone dry then removed the parchment and broke up the dried starter into smaller pieces which I then ground with a pestle and mortar. I put the resultant coarse powder into a plastic container and dropped it in the freezer (I don’t think it is actually necessary to freeze it unless you wish to keep it for a very long time).
Upon my return from the US I took ½ teaspoon of the powder, added 1 tablespoon of warm water and let it stand for about an hour before adding a tablespoon of white bread flour. After 24 hours at 30°C it was showing signs of coming back to life so I fed it with another tablespoon each of white flour and water. After another 24 hours it was definitely active so I reverted to my normal method of working by weight rather than volume using my normal feeding mix of 200:60:30 (by weight) white/wholemeal/rye. I weighed the starter and added about 1½ times by weight of flour and water.
Just to be safe I continued feeding every 12 hours for a couple of days, discarding starter as necessary. Then I reverted to refrigerating the starter and feeding every 4 or 5 days.
My first loaf using the resuscitated starter is in bulk fermentation at the moment and, judging by the way it is rising, it seems as healthy as ever.
As my wife remarked, “isn’t nature wonderful?”
I travel to SE Asia every year for 5 or 6 months at a time. I prepare air dried starter just as you describe and just store it at room temperature. I also just make up around 500 grams of regular starter, but at around 70% hydration instead of my usual 100%. I just put this starter in the refrigerator. When I return, the fresh starter isn't looking very fresh anymore. It has a dark layer on top and some hooch, too. I just pour off the hooch and scrape off the dark layer until I get down to the nice white stuff at the bottom. I take about a tablespoon of this and make it up as normal, feeding/replensihing it every 12 hours. It may take a couple of days to come back to normal, but it always has. I have never had to fall back on the dried starter, but when I test it, it revives well. Yes, nature is grand!
I recently defrosted some starter that I had stored in the freezer for about 4 months. After about 5 feeds over a week it produced a loaf just like normal. I will put a fresh lot in the freezer every few months now that I know it comes back very easily.
Give some to a friend who lives nearby and get them into baking. Then you always have a source!