This is wireless comunity, so i cannot afford spare licences
The main reason this router left with no upgades are scripts that are running on it and which are vital for network. As new RouterOS changed scripting engine I did not want risking problems with scripts not working after upgrade.
Now, I copied scripts to other router with new RouterOs version and fixed them to work, so I guess upgrade won't do harm on them.
I asked about this because I saw here in several occasions that people recommended steps in upgrade, and also mention problems with damaging license or loosing license level during upgrade.