Yes, I've used the Enerigizer Lithiums in things and they do last MUCH longer. Not only that but they are super light compared to regular AAs. The extra run time is worth the slight extra cost and more than makes up for it. However, be careful. We tried them in an Etrac and it gave an over voltage error. Also, linear voltage regulators (which I assume all detectors use because switching regulators may be more efficient, but they are more costly and generate a lot of noise that would require extra components to cancel out)...But anyway...Linear regulators get rid of the excess voltage by bleeding it off as heat on a heat sink that sticks out the top of the chip. The more excess voltage there is the more heat that is generated. I would worry that the extra voltage could cook the regulator. Most regulators have a thermal shut down in them, so if your lucky after it cools back down it will work again...But I wouldn't take that chance.
On the subject of batteries. I hear a lot of people say they don't like rechargeables because they might lesson the performance of their detector because of the lower voltage. In truth it doesn't matter, because the regulator only allows a fixed amount of voltage (say 8V) to the circuit board, so higher voltage isn't going to give you better performance. They do this to keep the voltage stable, otherwise the detector's tuning would constantly drift as the voltage drops with battery drain.
A good high capacity rechargeable nimh (say 2500ma or higher) will outlast a store bought non-rechargeable battery most of the time these days in terms of run time, so I'd opt for those. They are also lighter than regular batteries which helps with weight. Me? I run a 3 cell lipo in my detector. They don't lose their charge sitting on the shelf. It's healthy and normal and not stressing a lipo to do a 1 hour charge time (that's pushing nimhs), and even though I'm using a lower capacity 750ma lipo versus my stock 1000ma stock nimh pack I get longer run times because a lipo holds it's voltage very high until the very end of the discharge, so it trips the low voltage cutoff later than a higher capacity nimh which drops it's voltage faster as it drains. A 3 cell series lipo generates 12.6V, so it's perfect to replace an 8 cell AA pack. A lipo is also MUCH lighter and smaller. Only problem is they require a special charger, and should never be drained below 3V per cell (9V total for a 3 cell series pack). Luckily my low voltage alarm on my detector sounds off at about 10.2 to 10.5V. I had to wire a little plug inside my regular AA holder for it to plug into, but the little pack fits easily inside the holder. I can move the little plug out of the way to run regular AAs in the holder if I ever wanted to do that again. Nimhs drain as they sit, so they need a top of charge if they've say sat for several weeks (or say a few months at least), while a lipo won't self discharge.
