In the past I have seen usufructo translated into English variously as “life interest,” “life interest trust” and “life estate.” All of these translations imply that usufructo is, by definition, always a grant of the use and enjoyment of property for the lifetime of the beneficiary.
This translation is misleading and may be patently incorrect in many contexts when, for example, usufructo is granted for a specific period of time (called usufructo a plazo, usufructo a término, usufructo temporal or usufructo constituido por tiempo determinado). An example of usufructo a plazo would be the usufruct of a dwelling granted to the guardian of a minor child until the child reaches the age of majority. In such cases usufructo may perhaps be rendered as “beneficial interest” or even “beneficial ownership,” given that “beneficial owner” is “one recognized as the owner of something because use and title belong to that person, even though legal title may belong to someone else” (Black’s Law Dictionary).
Usufructo is likewise often subject to a condition (usufructo condicional), being another mode of usufruct that cannot be translated as “life interest,” “life interest trust” or “life estate.” Indeed, usufructo may be subject to a condition precedent (condición suspensiva), such as usufructo granted to a son or daughter provided that he/she marries. Likewise usufructo condicional may be subject to a condition subsequent (condición resolutoria), such as usufructo granted to a son/daughter that will terminate if he/she doesn’t marry by the time he/she is thirty years old. These are admittedly silly examples but that, once again, demonstrate that usufructo cannot always be equated with a “lifetime interest” or “lifetime estate.”
In summary, perhaps it is best to translate usufructo (a secas) as “beneficial interest” and reserve “life interest,” “life interest trust” and “life estate” for situations that actually refer to usufructo vitalicio.
See more on usufructo here:
Léxico Jurídico Español-Inglés 
There’s a reason for the mistranslation, namely that the functional equivalent of the civil-law usufruct in the common-law system is a life estate. But as you rightly point out, a usufruct can last for a period of time that is less than a lifetime, whereas obviously a “life estate” in the common law lasts a lifetime.
In other words, the mistranslation comes from using the common-law functional equivalent (life estate) to translate “usufructo”–but as you say, that is not a good idea because they are only functional equivalents, not exactly the same thing.
If you google “usufruct” you’ll find lots of sites confirming what you are saying, i.e., a usufruct is similar to a life estate in common law jurisdictions, except that a usufruct can last for a specific period of time other than a lifetime.
I’m just trying to explain where the mistranslation comes from: equating the two “figuras jurídicas” when in fact they are only similar, not exactly the same. This shows how dangerous functional equivalents can be.
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Hi Tom,
That was exactly my point (and as you indicate) , despite being widely used, “life estate” is not really a functional equivalent of “usufructo.” Indeed, perhaps “life estate” should be reserved as a translation for “usufructo vitalicio,” while rendering “usufructo” (a secas) as “beneficial interest,” “beneficial ownership” or something closer to its actual meaning (unless, of course, the “usufructo” in question is actually for a lifetime, in which case “life estate” or “life interest” would be accurate).
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