There are very few cases where a strategy that fulfills the criteria on full data set doesn't fulfill the criteria on the partial data. So you can easily safe the time for the first calculation.

Imagine you have criteria for max DD and max consecutive losses.

If you have max DD of $200 for the full data set, it is not possible to have greater DD for the partial data. The same is for the max consecutive losses. If you have 6 consecutive losses for the full set, it is not possible to have more for the smaller set.

However the opposite is fully possible. For example to have 6 consecutive losses for the partial set, but after loading the full data, the losses to become 8.