What units is Page Life Expectancy in? I'm currently using the following query to get the Page Life Expectancy from SQL Server:

declare @PLE int

select @PLE=cntr_value 
from psql1.master.sys.dm_os_performance_counters 
where counter_name='Page life expectancy' 
and instance_name='';


The issue I'm having is I don't know if this is in milliseconds, seconds, or what.  The value I am currently getting is 88936.  This could be in seconds or milliseconds.

It would make more sense if it was in miliseconds, but this server isn't used that much currently so something staying in memory for 24 hours (88936/3600=24.7) isn't impossible.
I believe that it's in seconds.  I've got a script running a loop that's capturing the value once every minute and it's going up steadily by ~60 every 1 minute interval.