I have tried both blanching and not blanching before freezing Runner Beans, having "topped and tailed", then sliced them into 1" pieces. Like glallotments, I haven't noticed any difference. I found a bag which had wedged itself in a corner and was almost a year old, steamed them from frozen and they were fine!
There is a huge carrier bag waiting to be attended to at the moment and the plants are producing faster than I can eat/give away/freeze. I'm amazed at how fast the beans grow and convinced they grow over-night, as I picked shed loads on Wednesday night and left only little skinny things. Thursday afternoon, the plants were festooned with huge beans! Magic!
And, how is it, you think you've got every single bean....the next time you look, there is some absolutely huge things which would be awful to eat!
Cheers.