Twin NDB, I think the Shrike and the Aerostar are the only GA twins that have pressurised power brakes.
The answer to how many brake applications (assuming Hyd failure) from a fully charged accumulator is ONE, so you need to think what you're going to blow the accumulator charge on, i.e., one shot of the brakes, or flaps, or even whether you want nosewheel steering. These can be your options and need to be considered, coz you've got to decide which facility is most needed.
A long runway won't need flaps or brakes, so you've got steering till you use up the pressure. A short runway is a problem, you need flaps and brakes. Fortunately the gear has a back up emergency system that's really good.