1- LUD means "latest update". If you have a receipt number, you can create your own portfolio on uscis.gov (
here). This is helpful because 1- they send you an email whenever your case status has changed, and 2- you can track LUDs if you want, but many times LUDs are meaningless; every time somebody at USCIS picks up your file or moves it to another shelf or something, there is an LUD change but it doesn't mean that your case is being processed yet. LUDs are helpful to some because it sometimes indicates that an approval is imminent, or if it happens soon after fingerprinting, that USCIS has received the fingerprint report, etc.
2- Some people filed I-485 when their numbers were current, but then the visa numbers retrogressed while their cases were pending, making a visa number unavailable to them. Such cases are still legally present in the US but cannot get the green card approved until their cases become current again. In cases where severe retrogression occurred, yes, they would require multiple EADs over several years.
3- Depending on which service center received your wife's EAD application, it will take anywhere from 60 to 90 days.
