Continuously running scripts question

[jyoung79 at kc.rr.com]

Currently, I have some scripts (in particular, applescript 
'stay-open' scripts) that run continuously on a Mac through 
the day.  They look in a certain folder every 30 seconds and 
perform the necessary work needed.

I was curious if anyone here on the list does anything similar 
with Python?  If so, do you use launchd, cron, etc in order to 
start up your Python script at the appropriate time(s)?  Or do 
you just let your Python code run continuously?  I'm curious of 
the pros and cons with each of these.  I'm assuming launchd (or
something similar) is probably the better option since if a 
script broke it would start it back up again the next time 
around.  Launchd also probably doesn't use as much processing 
power?

Thanks. 

Jay