I tend to make a lot of assumptions, educated guesses, while making mead and then investigate later when time and opportunity affords. Re-hydration, starters, yeast population, are on the front burner with me right now. Here are my thoughts so far:
1. Scott Labs has an excellent detailed procedure in their handbook on re-hydration. It talks about atempering your yeast before pitch so you won't shock it.
2. Directions for using a smack pack suggest atempering around 68*-70* and pitch to 5 gals with an SG of up to 1.060. But recommends pitching additional packs if your must is colder or your gravity is higher. Nothing about acclimating, just pitch more. Maybe there's an acceptable kill rate?
3. Starters are lag time environments. Populations in a starter will reach levels dependant on available nutrician and must volume (maybe the same thing). In my opinion, what is often overlooked is that when the starter is eventually pitched, not only has the population increased, it has aged. It's not young anymore. No more young cell walls susceptable to "burning" by DAP. Maybe not as susceptable to osmotic shock either.
4. Starters reduce lag time, they don't eliminate it. But your starter population is hardier, and therefore, healthier.
5. I currently mostly believe there's no need to do starters for powder yeast if you can simply rehydrate more yeast if there's an acceptable kill rate, a die-off rate that won't affect the growth and sustainability of the population. $1 per 5gms packet vs $13 per smack pack. If I could justify it, I'd just buy more smack packs and forgo the starter.
6. What I don't mostly believe, and this is begining to bother me, is maybe starting powdered yeast is a good thing too. Even though there is an acceptable kill rate, the thing that killed them must be stressing at least some of the survivors. I know we're talking billions here, but millions of those is significant. If I could baby them through a starter and acclimate them as bernardsmith suggests, reducing stress even more, wouldn't I have a better mead?