Best practice for specifying an interval

[Mark Morgan Lloyd <markMLl(dot)pgsql-general(at)telemetry(dot)co(dot)uk>]

I notice that section 9.9 of the manual has examples including both HOUR and 
HOURS, but the list of reserved words includes only the former.

Am I correct in assuming that

	select time '11:00' - interval '3 hour';

is preferred to

	select time '11:00' - interval '3 hours';


In a similar vein, are fractional hours best specified as

	select time '11:00' - interval '3 hour 45 minute';

or as

	select time '11:00' - interval '3.75 hour';

or with the interval converted to an integer number of minutes?

All these forms appear to work. I've got no intention of jumping ship but am 
curious as to the favoured and most portable style.

--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]