You could create select from source so instead of having thw WHERE in the LOAD part, you have it in the SQL part, using the DBM dates functions. The result is two QVD files, one with 8 weeks, the other with the whole data. Or you do one load unoptimized with these 8 weeks, and store this reduced files into another different QVD files, so the next time you reload you reload from the reduced ones. Even using a variable or something in the file
SET vAllData = 1; // 1 will load from the complete QVD, 0 will load from the reduced QVD you have created with this where.