Originally Posted by federali
It's my understanding that companies do runs of .35 Remington in time for deer season as there's little demand for this ammo any other time of the year.

For the longest time that was true, but for quite a few years there was a drought when manufacturers just stopped making those seasonal runs due to higher demand for other products. Now it appears they have resumed production of the 35 Rem, but only recently so. Hornady has also stepped up to support some of these niche cartridges as well.