This was my first shortage; I've only been reloading for three years. Powder has been the hardest to find followed by primers, bullets, and brass in that order.
I only reload 9mm, so comments relate to pistol components.
I want to have a two to three year supply of powder, a one to two year supply of primers (closer to two), and close to a one year supply of bullets. Towards the 2016 election I may increase my stock replenishment. I don't think you have to have equal amounts in stock if primers and bullets will appear on the shelves before powder. OTOH, it doesn't hurt.
1) find powders that are close to my favorite in case I have to switch. This can apply to bullets as well.
2) email notifications of availability are useless. Everything disappears by the time you read the email.
3) gunbot is useful, but you must be looking at it when the item shows up. You have, at most, 30 minutes to order.
4) auction sites are scalpers. I won't pay 3 - 4 times the regular price.
5) there's no downside to overstocking because you can always sell it.
6) even buying locally you have to be lucky to hear about a needed component becoming available.
Question: in previous shortages was powder also the last component to show up?