As most decisions in life, there are trade offs.
Here's my take.
Premium alkaline batteries typically will last longer than the average capacity rechargeable NiMh's.
The discharge rate of alkaline's for a lack of a better term is more linear than NiMh's. NiMh's discharge rate is more exponential meaning it'll provide energy up to a point then rapidly lose voltage.
My typical detecting sessions last around 3 hours before i get tired and need a cold one. I have never had them die during detecting which includes the occasional 5 to 6 hr. sessions. In my case hi capacity rechargeable NiMh's are a perfect solution and i would also say more cost effective.
For those who have much longer detecting sessions, only hunt occasionally or are in remote areas, alkaline batteries might be a better solution than rechargeables.
To minimize battery drain, i always shut the machine off when BSing with someone or during extended digs, use headphones and keep the volume as low as possible.
One of the heaviest battery drains for modern detectors is the audio.
Headphones are electro mechanical devices which need voice coil electrical energy to physically move the sound producing diaphrams in the headphones.
I've noticed that when i use no discrimination in a dense junk area, the continual headphone squawking from junk IDs and falses drains the batteries quicker than using a tight discrimination pattern with lower sensitivity which produces mostly nulls.
