A quick question for those in the know, everyday I pick up the guitar for about an hour of practice, and every day the guitars out of tune. Now it's a Yamaha Pacifica 612 and it's only 2 weeks old.. I've read that with new guitars it can pay to replace the strings straight away because you don't know how long they've been on the instrument and that they could be "worn out/stretched" before you even get to play or is this simply the case that you have to retune them constantly.

Thanks in advance