Yes you will get a chemical slide, even IF they duro more !!Not are durometer readings are apples to apples. Are you seeing signs that your tires are too soft?
RP had good advise for you about cycling the tires as much as you can by running them or storing them in a place that gets hot.
Are the guys with the harder tires winning and are they running thick or thin rubber?
You might be surprised with the hardness on the aggressively prepped tires if they have sat for awhile. While these may duro the same hardness as a light or no prep tire they will lack grip.