I've used some generic blue led modules to build a big clock with 7 segment displays.
This modules have 5 piranha leds and resistors in a weatherproof enclosure (a brick of molten plastic).
Modules look like this:
They are rated for 12V, and a real datasheet is not available.
After a year and a half of constant use, I've noticed that some of the leds are burnt, and most are not as bright as the new ones.
Without a circuit diagram it's hard to say what's happening.
Usually dead/dim LEDs are the result of people not using the right resistors to regulate the current. They might be overdriven to make cheap LEDs look brighter than they really are.
Some designers seem to think it doesn't matter if LEDs are abused this way, that if an LED survives for a week it will survive forever. Even some members of this hallowed forum seem to think this. The reality is that damage from overcurrent can be very gradual resulting in products like this.
The display uses a sheet of white hight impact polyestyrene as a diffuser, and I've noticed that it turned light yellow where the led light it.
So my first suspicion is that the modules are dissipating heat, and this is shorting their life. Or is it the UV light that yellowed the plastic?
Modules are not warm to the touch. And there is no sign of heat on the MDF piece they are glued with hot glue. The sign is place inside, and summer temperatures can go up to 32 degrees celcius.
If the yellowing is only where the LEDs are then the LEDs are probably producing a small amount of UV light. "Blue" isn't very far from UV in the electromagnetic spectrum. Even a small amount of UV adds up over time.
Would SMD LED strips last longer?
SMD LEDs are no more resistant to overcurrent than regular ones are. What you need is better current regulation, not a different type of LED.