The reason I made the point about auto-starting programs like PE, is that, unless you do, you never get full benefit from the program.
Using abbreviations has to become an instinct. Every time I type any personal details, or give standard replies to emails, or write a signature, or leave eBay feedback, or use a letterhead, or write a date, or start a program, or use a special character, or create an appointment in my diary, or minimise a window....I'm using a text abbreviation.
Programs like PE or Autohotkey are programs you have to commit to if they're really going to save you time. But once you do, you work in a different way. Every time you do something on a PC more than once, you ask yourself -- can I turn that into a text abbreviation?
The limit is really the number of abbreviations you can easily remember. If the abbreviations/hotkeys are sensible and intuitive, the number can be quite high...