I have a 128GB SSD in my 2011 MBA and every 6 months or so i have to keep deleting things to keep it from filling up too much. Ok so next time i'm getting at least 256GB but for now what do you suggest. I've noticed that as the SSD falls to around 20GB left the system starts to slow down, spinning wheels in safari, bit clunky opening things. I'm not swapping in/out and CPU usage is clear. When i first got my system i had around 105GB of free space. Even after offloading data into itunes match, not keeping anything in itunes and moving my iphoto library to an external drive i only have 66GB free. 10GB are used for apps, so the rest is just accumulated cache, application support small amount of docs and system stuff. I also have 37GB of back ups which dont show in finder but do appear in disk utility so i'm wondering if that hidden used space is contributing to it slowing down a bit. I can easily clear that by disabling back ups locally but any advise on cleaning up system caches and other unused files? I'm wondering wether to do a clean install but i have no quirky issues with ML and its a right pain in the ass re-installing everything, especially as i use this machine for developing and i have a workflow set up and key pairs. But on the other hand it might be a good exercise to clean off anything i dont need daily. I'm just unsure of time machine in case i connect the same drive to a fresh clean machine i might not be able to selectively restore some stuff. Never done it before.