Ceri JC

Really cheapo sleeping bags are generally only good for sleeping indoors, or in tents in summer (although if that's all you want them for, they're ideal). As you start to pay more, they can survive colder and colder conditions. I have never slept all night with mine done up all the way (it gets too hot), even up high up in the Swiss Alps, or in the depths of winter. Not bad considering it's over a decade old now and sleeping bags do go 'off' with age as their fibres get crushed down, even if you store them properly.