Are you going to be mounting the LEDs to a heatsink? If so I would actively cool them with something like a 40mm CPU fan mounted to the sink. I would not take the chance with them being passively cooled. active cooling would extend the life of the LEDs greatly.
Depending on what model xt-p or xp-e or the other models Cree makes you can run them at 1a no problem for years straight.
A lot of high end aquarium lights are now being made out of high powers LEDs
3w, 5w and even pendent style lights with 100w LEDs chips and they last for years.
Brigelux...