If you are listing for 4 days * 10 that is a 40 day run (astounded at my maths prowess?).
The simplest solution to keep them all running is to run Bulk Edit on all your listings once a month and bump the AutoRepost count back to 10. That way the count would never reach 0 and listings close.
An additional benefit, which might be useful to you, is the listing ID numbers and links to the listings would not change - as they would if they were allowed to close and then be reposted.
P.S. Always best to Export your listings as a backup before running Bulk Edit just in case it or you screws up.