I am probably the worst for this, but when I find something I like, I do my research and find out all the details about a product before I go all in. If there is a special or sale on certain boards or there has been a one off production, then I get to work and try to track down who has them and even contact the supplier about production numbers, distribution, etc. It has worked for some things. Quite often there are a lot more than you might think, or there are going to be more in the future so you don't have to worry as much.
For decks, if you buy as many as you can afford or find, they might last a long time but remember to store them well, eg flat in cardboard shipping boxes or something similar. I still have decks that are 10+ years old and they are still perfectly fine as they have been stored well. I know others who have decks less than a year old and they are done before they even skated them, because they left them jammed up in a cupboard or in their car, they have warped or have heat stress and become brittle and snap easily.
Right now there are huge shortages in the hardgoods side of the skateboard industry, some companies and brands more than others, or more so in some countries than others too.
What is it that you have found that you want more of? There are people on here who know a lot more than you might think (certainly a lot more than I do) and they can help you as well.