Aqua One 620T lights

Hi all.
It's been a bit over a year since we bought and set up the AO 620T for our discus. They seem to like the setup to the extent that we have discovered we have a breeding pair (tho the tetras scarfed the eggs :( )

I was wondering how often one should replace the lights in an aquarium?

They (the original lights from when we bought it) seem to be working ok tho a couple of them have started to flicker a little round the base. There's also a bit more algae round these days...the 2 siamese, the bristlenose and the whiptail can't seem to keep up...and I remember reading somewhere that weak lighting gives more algae.

I'd appreciate your thoughts :whip:
Thanks
The Zigster