If you look at them and they aren't leaking you can use them,but they' will likely not work as long as new batteries would.
not long
Patents last 20 years. Kramer's patent, US4667088, expired in 2007 but is still cited in new patents.
It all depends of the type of batteries and what you areusing them in.
about an hour
Rechargeable batteries usually last 300 to 500 cycles which is when a battery is at 100%, then is drained to 0% and charged again. Even if you do not drain it completely and recharge the battery, it is still considered a cycle.
Lithium batteries can last one and-a-half to two times as long as NiMH batteries.
Over 90 days im not sure of a exact number.
For the most part batteries brands do not make a huge difference but there are some things to know about purchasing cheap batteries so you can ensure you get the most bang for your buck. Always check the expiration date on the package. Batteries do not hold a charge long after their expiration date. Expired batteries are most commonly found at discount retailers. Alkaline batteries last considerably longer than regular batteries so if the dates are not an issue always go Alkaline.
Rechargable batteries will not last as long as normal AA's, but, of course, can be recharged, and should last over a year.
The batteries in an Xbox 360 controller are rechargeable. When full charged, they will last several days. The batteries themselves are meant to last the life of the controller.
Rechargeable batteries that are not charged for a long time will still work sufficiently. Batteries that are overcharged will damage the battery.
The batteries are over the counter watch batteries and they last twice as long as the battery put into the walker