simplify case statement with function?

I have a case statement that is quite long to write!

I'd be greteful to know if I can simplify this by using a function, and
if so how I would go about 1) defining it and 2) using it.

Thanks for any help.

select id, idtext, title,
case when n_msgs > 0 then n_msgs else 0 end as n_ms,
case
when
ceil((extract(epoch from current_timestamp) - extract(epoch from ts_modified))/ (60 *60)) < 2
then 1
when
ceil((extract(epoch from current_timestamp) - extract(epoch from ts_modified))/ (60 *60)) < 4
then 4
when
ceil((extract(epoch from current_timestamp) - extract(epoch from ts_modified))/ (60 *60)) < 8
then 8
when
ceil((extract(epoch from current_timestamp) - extract(epoch from ts_modified))/ (60 *60)) < 24
then 24
else
2000
end as hours

--
Rory Campbell-Lange
<rory(at)campbell-lange(dot)net>
<www.campbell-lange.net>