As time goes on  

If you really love design, learn as much as you could to the point that sometimes it feels like a curse and you will know when you are there. When you spot something anywhere or a part of something is sticking out of the dumpster, your brain starts to work identifying the item, naming the designer, the manufacturer, when it was designed, the story behind why it was designed, why it is not a knock off and what kind of restoration it will need to get it back into shape again.
Avoid trendy stuff if you can, prices are high because there is a demand for those items. Focus on what appeals to you regardless of trend, pedigree and you have a use for those items.
Say no to free and if you have to spend some of your hard earned income on something, get the best (and the rarest if possible) that you can afford and never get into debt on anything just because you have to have it. Acquire what you need, not what you want.
For me and I am sure there are many out there too, my interest in mid 20th century design started to slow down back in the mid 1990's when manufacturers like Knoll, Herman Miller and others started reissuing many of their long gone discontinued modern icons from decades before. Unless I have a use for it, it is unwanted and free, it is not common or ubiquitous and has not been reissued, then I will make room for it.

If easy access to the internet is the problem (which leads to financially motivated falsehood), then easy access to the internet is the solution. Use the internet to allow the buyers to educate themselves, and they will fix the sellers.
You, also might find that there are unknowns from the era who deserve re-discovering. I am sure there are many more Irving Harpers of the world.

Kyle,
It sounds like your intensity and immersion in collecting was burning so brightly that it was only natural to expect a little cooling-off for a bit.
And nothing can compete with that "first awareness" time in one's life-- that first wave of discovery when one thing leads to another and the learning curve is so high and fast that it's just like some kind of rush that lasts for years.
For me a little "lag" in my intensity has happened twice in 30 years of collecting. It might just be one of those, so don't worry. As you have expressed, you're down, but still in it for the long- haul.
With the huge popularity and resulting awareness and appreciation of mid-century design by the masses, finding stuff at the thrift stores is not gonna be like shooting fish in a barrel anymore. But all of your knowledge acquired up to this point will serve you well going forward, and make you more able to see a good thing when it happens, whether it be on the internet or at the corner yard sale. (Or with time and age, maybe just the ability to see the difference between the mid-century "craze" and the timelessness of a good design.)
Every time my enthusiasm for collecting great design wanes for a few moments, I only have to look around the world and see the endless ubiquitous visual noise that is so hard to look at, and I realize how exciting it is to create at least one environment where everything flows and life is beautiful.
The money part, I don't know, it used to add to the excitement of a find, and still does, but in the end it's the THING (and the historical conversation and/or argument about the thing) and the life it had in the world. Looking at something that doesn't hurt your eyes counts for a lot, and looking at that rare thing that is outright ALIVE with inventive good design and character-- is endlessly enjoyable.
Sorry, its early and I ramble…. thanks for bearing with me!
Glad to hear you are in it for the long haul.

All of the above, plus this. I got in on this about 18 years ago, before the big wave hit, and I used to get a lot of good stuff at junk auctions for next to nothing. I quickly amassed more stuff than I or my family needed, so I started selling the excess. My problem was that I felt like I had to own all the beautiful things---if it do-able then I went after it even though I didn't need it. I also liked EVERYTHING at first---American modern, Danish modern, all of it.
Then I realized two things:
1. It was enough to just see the thing and enjoy it in that moment without feeling like I had to own it, too. It helps a lot that I have friends with a big MCM shop and I get to visit things there all the time and appreciate the beauty and craftsmanship of great furniture. I've also gotten to restore a lot of good MCM chairs for people, some of which were/are rare and especially dropdeadgorgeous, which is even more fun.
2. The style I liked best was Danish modern, for various reasons, which made it a lot easier to back off from the great American stuff (though, ok, I do have a little Saarinen tulip table that I love).
So I've reached a point where I'm happy with what I have, which are some very nice things, and don't feel like I need anything else. I might switch out something for something else if it's a good deal, but that kind of thing happens less and less often and so far it's been a pretty close contest when it does happen.
I do still buy the little stuff, though---painting and drawings, pottery, textiles, art glass, teak objects---stuff like that. I think those things are what make a home your own in the end, I remember back when I used to look at endless photos of MCM interiors and reaching a point where it seemed like many of the owners simply had a checklist of iconic pieces that they had acquired. The places all looked the same. Then there are homes with iconic furniture (or just good but lesser-known designs) but are very personalized with art and stuff---those are the really interesting ones, the kind I want to look at and visit and live in.