Yes, the Doppler information is always written in the binary files. If you use the NMEA mode you will get it too but it does depend on selecting the correct sentences (NMEA items). Use the binary made. It is better.
The data logger can save up to about 7 hours of 1 second logging binary data but I don't know exactly how much and it depends a bit on what logging options you choose (no logging below a certain speed, etc)
I have one 265mb SD card that contains all my sessions for the last 12 months and is still half empty. (Binary format logging with both SBN and SBP files for every session) :)
The reserved items in the menu are for future functions.
Don't use the NMEA mode. The Binary mode is much more efficient and contains all the data we need.
Hope this helps, Andrew