Well you are asking several things.
I had one leak and 2 others that never have, Adagio has a video on how to completly take them apart to clean them. You should probably try that first. They say it stops the leaks. Unfortunately I found this video too late.
How long the filters last, before what? You can buy replacement filters, but I'm not sure why you need to.
As for floating - you need to rough up the outside edge of the filter. At least that is what I do. Funny I just posted on this recently. If you scuff up that edge pretty good all the way around it fits snug again.
Are you putting it in the microwave? That might be part of the problem.