Quoting from Word Help:
Length of AutoText entry names (including spaces):
32 characters
Number of AutoText entries per document template:
Limited by template (template: A file or files that contain the structure
and tools for shaping such elements as the style and page layout of finished
files. For example, Word templates can shape a single document, and FrontPage
templates can shape an entire Web site.) file size and/or available memory
Number of global AutoText entries:
Limited by template file size and/or available memory
