Anyone who owns an LG smart TV must inform all guests and family members that they are being monitored – this is required by LG’s current terms of use. Meanwhile, LG monitors install potential malware and surveillance software on a connected Windows computer.
The only technical explanation that’s not malice would be that some certificate store on the device had expiring certificates and would need an update to continue to function (or rather connect to remote servers).
Are there ever certs that expire in 3 years?
Yes. Certs can expire after whatever time the issuer wants to set for them. That could be six months or 20 years. Some infrastructure has limits on max and min lengths (more max than min usually) but not all and there are best practices as well.
More importantly the certs could have been five years old by the time this person got the TV for a total age of 8 years.