How do you know or find out if a company is going to stop producing a product? My hubby and I have started visiting National Parks using the National Park Passport. I want to use the Year.O.Graphy collection by Simple Stories and I'm not sure if I should heavily stock up now or can I gradually by more along the way. What are your suggestions?

It's pretty hard to tell. Some companies produce the same papers for years and you can find them decades later. Some only produce a smaller amount and move on to other collections. You could write the company and ask how long it should be available, I suppose.
Also, companies go out of business suddenly, so there's really no guarantee. If you only want to use that collection and nothing else, I'd probably get it while you know you can.

Speaking from experience from a Simple Stories user...I'd start buying and stocking up now! They are a relatively new company and just a few months ago they already started discontinuing some of their first lines they introduced--including the one that I need to replicate an album I made for myself so I have one to give to my Dad. I've been lucky and can still find most of what I need (from the 100 Days of Summer line), but there are a few sheets that I can't find any extras of.

But in regards to lines/companies in general, even if a company doesn't discontinue a line some stores don't reorder all or parts of a line because there's always something new and wonderful coming out that they need to make room (and inventory $$) for.

So really, if you know you like it and will need it, I say get what you can while you still can.