I think they do but only when combined with other acts such as less constant advertising of products. This would be the equivalent of saying AA meetings don't work, whilst permanently waving a bottle of alcohol in someone's face.

I would also say buy less, buy only what you need to replace and can't be repaired, and buy more sustainable and long lasting, are three different tactics, that can all work together but can target different people individually. There will be different socioeconomic factors that perhaps affect which theory certain groups of people go for.