Wow, that thread was chock full of nonsense.

As far as bleach losing it's effectiveness, let me put it this way. All bleach solutions (a combination of Sodium Hypochlorite and water) contain water right off the shelf. To say that water has some adverse effect on the solution is not supported by the facts. Contaminants in the water can react with the chemical to liberate some of the chlorine and weaken the effectiveness, and it will off gas and lose its concentration in an open environment, but if it is in a closed container mixed with clean water, it will not diminish any more than the initial dilution when it was put in the container. If you have it in a spray bottle, it will remain approximately as effective over nominal time usage as long as the seal is reasonably good and no contaminants are introduced.

Heating the solution doesn't directly effect the chemical, other than evaporating it, which if it is in a contained system will only recondense back into solution again. In the washing machine, hot water will evaporate the chemical out of solution quicker, but not at a rate sufficient to diminish the effectiveness of the application.

Sunlight can ionize the chemical, much the same as it does water, into it's elemental compounds (sodium, chlorine, hydrogen, and oxygen). Unless the sunlight is concentrated, this process is relatively slow.