The current recommended firmware for the ZD1200 is 10.2.1.0.183 MR1 refresh 5. The latest firmware is 10.5.0.0.212 GA refresh 2. Why is the recommended firmware so many versions back? Is the 10.5 firmware still acceptable for production systems? Thanks in advance.
New firmware adds new features. It also often limits how old AP can be used. On latest firmware you can use only 802.11ac W2 and 802.11ax APs, all other are not compatible.
In most cases, features you have in older version are perfectly enough, so except if you get problems, need to add latest APs, or need new features, upgrade isn't really that necessary, and in some cases is just not possible (if you have 802.11n APs, for example, and don't want to bin them).
Adding APs to an older system may be a problem -- currently you can buy only WiFi6 APs, and, for example, with R350 it means that you absolutely need the latest firmware -- so if you have 802.11n APs on your system you need to look what you can connect, before buying new AP...