Manufactured products tend to have two spikes in their failure rate: soon after being put into service (manufacturing defects showing up when the product has been used a bit) and near end of life (parts are wearing out due to long usage). In the middle, the failure rate is pretty flat.
Monitors failing within 3 months suggests that you're seeing the infant mortality part of the curve. If a particular monitor lasts 3 months, it will likely last for many years.
Tangentially related, but still interesting: most people think hard drives have a bathtub curve when failure rate is plotted against time. Turns out this isn't true.
Schroeder and Gibson: "Contrary to common and proposed models, hard drive failure rates don’t enter steady state after the first year of operation. Instead failure rates seem to steadily increase over time."
Monitors failing within 3 months suggests that you're seeing the infant mortality part of the curve. If a particular monitor lasts 3 months, it will likely last for many years.