Do you teach from a computer? Do you hit the power button and have enough time to run to the copier and put your lunch in a fridge before it reaches the log-in prompt? The first step in regaining some sanity is to roll your own teaching station. The second is to invest in a solid state drive. In a couple years this discussion will be moot, as solid state storage is trickling into more and more computers by default. But if you're sitting there aggravated at the 30 seconds Word takes to launch in the middle of the lesson, this is the upgrade for you. Prices have been falling for the last year. I bought a 256GB Crucial M4 in June for $250 and it's already gotten cheaper.
I'll let the results speak for themselves.
Traditional spinning hard drive:
And the magic of solid state:
This small purchase easily added 2 years to the life of the laptop I use. Think of me next time your standard issue is giving you fits.