Good to have always updated version of code for Security reason.
couple of questions :
1. What is the current Version running.
2. you need to look upgrade path if you are jumping from lower version to higher version.
3. what is the model of ASA you are trying to upgrade.
4. Need to read the release notes, your features all covered and no bug reported in the realse notes.
5. If all above satisfies.
Main Upgrade :
1. Chosse the least effected area you can upgrade, in case any issue you can degrade.
2. If the Device running More than 2 years, please do reboot the device before upgrade,
3. Make sure you have all the backup of config up to date.
4. Do upgrade always in Maintenance window.
5. Once 1 device upgraded, i prefer to wait for 2weeks safe side no issue reported and you monitoring that side constantly, then good to go for another device upgrade, this tiem you wait for 7 days to monitor.
6,. if above 2 devices stable, do rest in the process.
here is high level steps to upgrade : ( since we do not know the extiing verison, steps are genric)
http://www.balajibandi.com/2019/02/26/asa-os-upgrade-active-standby/
