Does anyone have info on expected success rates for thawing of frozen embryos, in particular blastocysts?

I'm not really finding anything, and just feeling a little bit concerned that only half of our first batch of embryos thawed. Is this normal? Should I expect similar with the second batch that are in the freezer now?

It's all a little bit depressing at the moment - my tendency towards hyperstimulating doesn't allow me to have fresh transfers.

BW