I think a couple of options are available, you could put checks within the script to see if there is an error and add a loop to try again after a sleep period, or another option would be to use a single script that had the logic to decide if an up change or down change is required and use the jcs: dampen() to limit the number of simultaneous executions and handle accordingly.
I've not tried this myself before but these are the types of approaches that I'd look at.
Not sure if I have time to try this out just yet, but I'd also have a check on the wiki pages and see if this has been discussed before, I think that it may have been already.
Regards,
Andy