I am not sure how viable on keep buying the "exclusive" sets are anymore. Everyone and their dog is doing the same thing with articles being written about investing in Lego is better than gold. How many of these $400+ sets can you sell in a year? The target audience is dwindling to the rich and serious collectors. Then comes the worry of fraud on these high end sets. Having a few are nice, but not sure about being a major portion of a portfolio.
Where as if you can pick the right ones under the radar sets at MSRP between $25-60 hope it appreciates to $50-100+ set where it is still affordable to most grand/parents, uncles, aunties, god mother/fathers etc. buying these as gifts for kids you maintain the huge intended audiance. You can probably flip more of these and have less headache with storage. Perfect example from 2015 is probably 75920 Raptors Escape. Yes it was a Wal-mart exclusive but there were plenty available in Q4 of 2015 for people to load up. Those saw the opportunity were able to cash in during the summer shortage and Christmas madness. Today, this set is going for $95 on Amazon, yes a dropped from it's peak but still much higher than MSRP.
This year, I am keeping watch with sets in this price range and load up on it and reduce the amount of $200+ sets.