You are looking at it from one perspective, to run the original pub, in its original range, with the DPs generated from a lower range.
There are 9 million ways to skin a cat.
I am sure you have done this kind of test and analysis, so answer me this, if you reuse DPs found during a 66 or 65 or 70 bit range, to find a key in the same exact range, how much search time did it take, was it less, if so, how much less, on average?
It's not as easy at it sounds. If the jump rules stay the same (so the DPs can actually work between different intervals) then the DPs are valid and usable, but unfortunately the interval doubles in size for every bit increase. So where are the DPs that should cover the newly added other half? Nowhere.
To get the optimal runtime, the Tames start somewhere around the middle of the interval + some common offset (so they are all, on average, to a minimum closest distance to the Wild/private key).
But what we have, are DPs of kangaroos started from the middle point of the first half of the new interval (around half of them passing into the second half of the new interval). And also the DPs converted from Wild distances after a solve (all these DPs will start from where the private key was in the old interval, so we don't know what they cover).
So now we should run new Tames to cover the second added half (traveling a double distance than what Tames did over the previous interval). And we also need Wilds that need to cover the entire new interval (since they can be in the first or the second half of the new interval).
Since jumps are the same, the jumps need to be more of them! Usually, if the interval increases, we do longer jumps, but this breaks DP re-usage.
In short, existing DPs would help, but only if the private key is in the first half, not the second. And only if the jump rules are kept and don't affect too much the expected runtime.
Repeat for every new bit added... for 5 added bits the interval is 32 times larger, So I guess my math is wrong, it will take sqrt(32) more operations to solve, but the DP coverage of re-using the previous DPs is very low, not 17%, if I'm not mistaken... I think my fallacy was that I was assuming that if you solved an interval, and you increase by 5 bits, than 17% of the work needed was already performed, but my fault was that 97% of the DPs required for this to be valid are missing, since all of the known ones are sitting in a very tight corner.
You try use saved files from kangaro of JLP ?