Correct/optimal DML query for application session management ?

Hi,

I'm probably being incredibly stupid and missing something incredibly
simple but I've got a bit of query-writers block here !

create table app_sessions(
session_id char(64) unique not null,
user_id char(32) unique not null,
session_start bigint not null,
session_lastactive bigint not null
);

The rules are :
Enforced session timeout after 86400 seconds (1 day)
Last active less than 1 hour ago.

My idea to clean out stale sessions :
delete from app_sessions where extract (epoch from
now())-session_start>86400 or session_lastactive<=extract (epoch from
now())-3600;

But of course that's going to be a nasty query, so that's why I think
I'm missing something and need a fresh pair of eyes (or a whole
mailing list's worth of eyes !!).

Thanks guys !