Garmin have only been producing GPSMAP devices with internal batteries for a little under 3 years now, so most of your 14 years of experience is not applicable to these models.
I would even go so far as to suggest that most of your 14 years experience would not be applicable to any modern Garmin GPSr that uses AA batteries either. Not only has battery technology come a long way, the electronics they power have become exponentially faster and far more energy efficient during that same time period.
Comparing battery run times between a 10 year old device and a modern device, each with time period correct batteries installed, would be like comparing apples with jellyfish. Pointless.
Do not allow your preconceived notions (and experience) to prevent you from enjoying all that modern technology has to offer.