sakoooot - my clinic doesn't do betas any more, so for this last cycle, they told me to test at home on 18 dpo (so 13dp5dt). In fact, I tested on New Years Day which was 12dp5dt and got a very strong positive. I would say the longer you can wait it out, the better, so that you don't have to stress about whether you can or can't see a faint line if you test early.
My first cycle, when my clinic still offered betas, I tested the night before my beta so as to be somewhat prepared for the outcome.
Me 35, DH 41
TTC 4+ years
4 IUI's, BFN
#1 IVF, 04/2009, BFN
#2 FET, 07/2009, no transfer, frosties failed to thaw
#3 IVF, 12/2009, +ve HPT New Years Day!
GEORGE THOMAS ALEXANDER born 18th September 2010, 9lbs 4.5oz. Our beautiful boy.