Do batteries in a device go dead if you don't use them for a while?

Depends on the device. Some slowly leach power from a battery and others hardly drain any at all.

(Your TV has batteries?)

@Zaku TV remote control

Batteries have a shelf life. It used to be approx 5 years & the package was labeled with the “Good until” date. I’ve noticed that over the last few years that the “Good until” date is no longer printed on the packages. It’s possible that your batteries were at the point of expiring even before you used them. I have had batteries explode inside the device when not used frequently!!! I can’t prove anything I’ve seen because the manufacturers have FAILED to admit. All I can tell you is MY experience over my lifetime!!!

The big threat to leaving batteries in a device that is unused for prolonged periods is in the tendency for the batteries to leak due to the pressure from hydrogen gas produced from chemical reactions within the battery as it ages. Eventually the battery ruptures and leaks. The leakage (corrosion) is potassium hydroxide, and is responsible for the ruin of more battery operated devices than any combination of causes you care to name or imagine. It’s therefore a good idea to store the batteries outside any device that is to be used infrequently.

Batteries die, in use, not in use, sitting in an unopened package in the junk drawer.
How quickly they lose power depends on several factors.
Leakage is indeed a nasty problem, and should not be touched.

Keeping them loose rather than in the device should help IMO or if arrange them in a manner that + and – aren’t aligned if having multiple batteries.

Sooooo, after the zombie apocalypse we only have a five years supply of batteries for our phones, phlashlights, etc. and after that we are in the dark?

Only those of us who haven’t been eaten.

@rojo Yep. Even with batteries, we will still be in the dark!!!

Yes, battery chemistry is imperfect and they will discharge slowly over time.
However, “sluggish” is Not a symptom of low batteries on a digital device. The symptom of low batteries on a digital device is OFF.
I’m guessing if you have not used them for some time it’s possible they are trying to update their software over the internet, and that can make them distracted while it’s happening.
Otherwise it’s also possible you just remember them to be faster than they actually are – or your ISP got slower due to more traffic or anti-network-neutrality.

@dabbler No – they were working but not correctly. What you’re saying makes sense but I changed the batteries and now it’s working fine.

Please, please, please get a cheap voltmeter. They are free at Harbor Freight if you buy something – even $0.99. I have them everywhere: garage, basement, tool box, barn, cars, hallway closet near batteries, etc.
A new AA or AAA alkaline battery should read 1.57 V or greater.
Depending upon the device you’ll still get some use out of a battery running at 1.4V (about 10% remaining capacity).
Below that value you can toss them without feeling too guilty. (I use them in flashlights until the run down to nothing.)
I always check batteries before I change them. Often the problem is just a dirty or corroded contact.