You consider all possible combinations but there are backdoors, I have recovered 11+ charachters for clients which you said would not be possible. Lets face it, math is not the only factor here, you have to be lucky sometimes too
That's why i said that it is a generic answer which itself is not true.
Under some rare circumstances, yes.. of course it can be recovered.
But just because i recovered a password '
123456789012345678901234567890', it doesn't mean that
every 30 char passwords can be cracked (which your statement implied).
I've heard there is a soft to extract password's hash from wallet.dat and then use Rainbow tables (which are already computed and ready for everyone on Web) to find out the relevant combination of characters. This way the necessary time will be greatly reduced.
You probably think of brain wallets (rainbow table) as there is no such thing determinating combination of characters from a hash, its not reversable.
The hashing algorithms does not have to be reversible for rainbow tables to be applicable.
The concept of rainbow tables is that you trade off computing power for storage space by precalculating the a big amount of combinations for further look-ups in this table.
While this is not applicable to a single wallet file, i still wonder why you have such a misunderstanding regarding rainbow tables. Especially since you claim to be a professional password recovery service