This is a general (hope not too general) question concerning the (future) use of the year and the date fields in biblatex.
The short version of this question might actually be: "Is it likely that the year field will at some point be deprecated and should I switch to using date?"
But I'm actually curious about it more generally. The biblatex manual strongly encourages the use of the date field over the year field. However, I've been faring fairly well so far with using year. I rarely need month and day, or some of the other fancy stuff like eras and things, so for reasons of economy, I have found it easier so far to only use the year field and then for the occasional "in press," "forthcoming," or "no date" to use
Year = {\bibstring{inpress}}
for example, as opposed to leaving Date blank and giving
Pubstate = {inpress}
(since date = {inpress} or date = {\bibstring{inpress}} don't work). Having a year together with an origdate field also seems to be working fine (at least for biblatex-chicago's author-date specification). So at this point I don't see a reason to change my database to date.
However, is there any particular reason why I shouldn't use year? Will it likely be deprecated in the future?