2011 MacBook Pro running very slow since OS X 10.8
My MacBook Pro has been running painfully slowly since upgrading the OS X to 10.8 (and subsequent updates, now up to 10.10.3).
In several programs, data entry freezes (my MBP can take up to 30 - 60 seconds to record each single key stroke). This happens in a variety of Mac (Safari, Notes, Mail) & 3rd party software (especially MS word & Excel), but it appears to only be in text entry programs (Adobe Photoshop, Final Cut Pro work fine, without these delays ever appearing).
Many programs take a very long time to load, and I will frequently get the "Spinning Wait Cursor" (for up to two to three minutes) when these programs freeze after first starting.
The freezing generally improves, after a while (my MBP seems to choke / freeze for a while - up to about 15 minutes; before returning to a normal response time for keystroke entry)
I often don't completely power down my MBP for a few days at a time, instead I put it to sleep by closing the lid while I travel, before opening it to re-start, which is when I often go through long periods of these freezes in various programs.
I've taken my MBP into the Apple stores numerous times over the last ten months, and the hard drive & the mother board has been replaced, but I still have the same frustrating keystroke lagging & text / data entry software freezing.
I only fill my hard drive to 90% of it's capacity at most.
Thanks in advance for your advice!
MacBook Pro, OS X Yosemite (10.10.3), 2.3 GHZ Intel Core i7, 8gb 1333MHz