Access a large table with a predefined index

I want to use a predefined variable to index a large array more than once. For example:

a = {i, j + 1, k-1};
b = {i + 1, j, k-2};

I know that I can do it in many ways, but for brevity in the formula, I wish to use double parenthesis assignment, such as:

Ex[[ Sequence@@a ]]+ Eyes[[ Sequence@@b]]

However, in a lot of calculations, the sequence operation adds about 50% more time. Is there a way to avoid overhead costs related to time? Thank you