I would have much more concern with the flax oil than the olive. Flax is almost always sold in dark bottles and you have to keep refrigerated. Other oils such as Olive or Canola are much more stable. I have no evidence, but would guess this will carry over into powdered form so my suggestion is to skip the flax oil.
As a single data point I will mention I always make up my DIY for a week at a time. I mix all my dry powders and then add the oil (canola and MCT) in a big bowl and mix until all the big clumps are broken up and all the powder darkened uniformly. Takes five to 10 minutes and I’m sure doesn’t mix as well as using maltodextrin, but I don’t plan on adding maltodextrin as a carb source. My DIY is now ready to scoop into a glass and stir with water when needed. I store the whole container of powder in the refrigerator so it stays cold and I have never had a problem with it going bad in the one to two weeks I normally use it.
On a road trip I did once have a batch unrefrigerated and out in a hot car for much of a three week span. It didn’t make me sick and I didn’t notice any change in taste or smell over the three weeks, so maybe refrigeration is unneeded. However both of my oils are much more stable than Flax. Back when I was researching what oils to use some articles suggested that up to 50% of flax oil bottles have started to go rancid before they ever get bought and you need to buy from a source that is both careful and has high turnover in the warehouse. Just not worth it for me, so I switched to chia seeds to boost omega 3’s.