Phusion in PCRs for TruSeq libraries

[hawaii454-0]

Hello,
Has anyone noticed a change in the number of cycles of PCR they do for TruSeq library preps? We've noticed that between 4 and 6 cycles are all that is needed to give a library quantity which can be sequenced. When comparing preps using the same control DNA from just a few months, there's been a definite decrease in cycles needed. Could this be down to the phusion mastermix working more efficiently? Has something changed in its make up?

Thanks,
Anna.