I started using the right Alt & Ctrl keys after my left hand began feeling strained from the Alt/Ctrl + Number routine. I actually removed the left hand Alt & Ctrl keys from the keyboard to discourage myself from using them, and after about a week, I had basically learned to use the right side keys without any issue (plus my hands feel much less strain).
The only time I continue to use the left hand Ctrl key is in conjunction with the mouse cursor - I use a ThinkPad, so it's difficult to control the trackpoint with the same hand (my right) as I use to hold Ctrl.