In contracts, the word indefinitely is used to convey two different meanings. I’m not keen on that, seeing as the Prime Directive of contract drafting is not to use one word or phrase to convey two or more meanings and not to use two or more different words or phrases to convey a single meaning.
One meaning conveyed by indefinitely is “without limit,” with the implication being that although a limit hasn’t been specified, one could be at any point.
Inspire may terminate this Agreement upon ___ days written notice to Novasep if Inspire, in its sole and absolute discretion, discontinues or indefinitely suspends the development and/or commercialization of the Product.
But more often than not, indefinitely is used to convey the meaning “perpetually.” I think perpetually itself conveys that meaning more clearly, in that there’s nothing that isn’t definite about forever:
During the term of this agreement and indefinitely [read perpetually] thereafter (with respect to any Confidential Information that constitutes a trade secret) and for one year thereafter (with respect to all other Confidential Information), Acme shall not (1) disclose any Confidential Information except as contemplated in this agreement or (2) use any Confidential Information other than in connection with evaluating the Transaction.
But those drafters who are fond of the picturesque from the beginning of time (see this July 2006 AdamsDrafting blog post) might prefer the oh-so-romantic until the end of time.
Note that when the notion of “forever” is followed by until, you can dispense with the word articulating the notion of “forever”:
Participant further understands that the Securities must be held indefinitely until they are registered under the Securities Act or an exemption from such registration is available.
The Company shall notify the Grantor as soon as reasonably practicable within such 30-day period if it has commenced discussions regarding a Business Combination with such suitable opportunity, in which case the relevant period of exclusivity shall be tolled indefinitely, until the Company releases such suitable opportunity pursuant to Section 1(c).
[Updated December 30, 2010: When you're dealing with an obligation not to do something, perpetually is actually not a perfect fit, as its everyday meaning is "nonstop," and that presupposes action, not inaction. (Think "perpetual motion.")
But I don't think that poses a problem. For one thing, there's no risk of confusion. And use of the adjective perpetual is entrenched in contexts not involving action—think perpetual license.
Of course, the simplest way of articulating the meaning "forever" would be to use the word ... forever. But a quick search on EDGAR confirmed that drafters don't use forever in connection with obligations. If a familiar word, perpetually, would get the job done, I'd be loath to recommend a novelty, forever.
And forever does have a certain fairy-tale vibe to it ...]