My gut tells me that accordion bottles are neither as good as the manufacturers would claim - nor as bad as their detractors would have us believe. I suspect that a 'squeezed" accordion bottle is more effective for a month or so than a partially full rigid container. They have their place but are not a panacea. It's clear from some of the posts here that some find them effective for up to six months. Personally I don't store stock or working strength solutions that long - but for a week or two I've found them very effective. This morning I was about to throw out some partially used print fixer stored in an accordion bottle for the past 10 days. Purely in light of this thread I tossed in a piece of old, unexposed Tri-X to check the clearing time - it was 1m 45 sec, which is about the same clearing time as fresh fixer for me. (I then tossed it!) To make this a true test, of course, I should try this with fresh fixer in accordion bottles and in full plastic bottles and in full and partially full glass bottles and then repeat with used fixer. But that's just not going to happen! The accordion bottles work for me and for the uses to which I put them.