Business continuity, risk, and IT standards
When you produce documents or spreadsheets or anything else, do you pay attention to its format? Are those formats ones that you can read later, if your current vendor stops supporting them, if they go out of business, or if they start charging more than you want to pay? That might be a question to ponder. For office software, there's an emerging standard. For articles, books, and other forms of text, there are standard XML formats (e.g., DocBook) and plain text formats (e.g., LaTeX).
Ask your vendors if they support such standards. If they say "Yes, with enhancements," be careful; an enhanced document is one that isn't standard.