Deflasking is not the problem...
It's the survival rate after 3 months out of flask that should be of concern.
Many seedlings will do fine within the 1st month. But depending on how strong the seedlings are, whether the environment you put them in suits the seedlings, how well the seedlings adjust to life outside a bottle, whether the flask somehow got contaminated before you were able to deflask them, how many seedlings you get per flask, or how on top of things you are with husbandry; your success rate with seedlings will vary all over the map for at least the first 3 months from being deflasked. It also depends on the type of seedlings you're talking about.
As far as a Paraphalaenopsis hybrid is concerned...
I think you might be fairly successful in deflasking and the period up to the first 3 months after deflasking. I've found that the seedlings of Vandaeceous orchids tend to be fairly strong compared to some other types of orchids.
Not to be a downer, but realistically speaking, don't be surprised that there could be a
possibility of a 100% rate of loss for the flask of seedlings you get though. Just sayin'. It's definitely happened to me before.
Good luck.