Bec,
there are differing opinions, but from what I've read, the majority of medicos believe that blasts thaw better than Day 2s.
But I gather that many clinics will only offer blast transfers to patients who have 'failure to implant' issues - like me
- or 'failure to sustain a
pg'. In the second case, genetic testing may be offered, as having to culture to blast is usually needed with PGD.
In your case, I'm sure that the fact that you were achieving implantation would make your clinic less inclined to change your protocol, IYKWIM. But it's something to keep in mind for your future cycles, and certainly researching your best options is the best thing you could do for youself as an IVF patient.
love
sushee