Hey Calvin. I am sure JB will chime in shortly. I don't believe the new transmitters are harder on batteries but are more sophysticated and may draw slightly more current than the old ones. I think the old Super Seven came with 500ma pack and the new Fasst T7C is 600ma.
When the Super Seven was out most all microprocessors used a 5volt supply where now the standard is 3.3 with some less than that.
I don't believe a guy needs to buy a new transmitter battery unless he plans on his transmitter being on for more than 2 hours on that day. I call it a day after mine has been on for an hour or slightly more. Transmitters are low current devices. Servos are what draws higher currents.
Typically you don't get a larger battery for your plane for more flight times but rather for higher loads. i.e. more servos or larger servos. Not talking about electric airplanes with electric motors here, thats a different animal.
Still however with a nicad or nimh in the transmitter it should be charged the night before you go the field.