I have one router in sensitive position so I avoided to upgrade before. It runs Mikrotik 2.9.51. Now, I need new options of MT on that spot so i am planning to upgrade to version 4.5.
Is it ok to upgrade directly to last version or I have to follow upgrade path using some intermediate versions?
Upgrading directly would be a one time operation, so risk is smaller. If you do many upgrades, the risk of a failure increases. You can make a similar router in your office and try how the upgrade works there. Only then attempt to upgrade the critical location
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.
I’ve upgraded several boards from 2.9.x to 4.5. I’ve done it:
2.x → 2.51 → firmware update-> 3.30 → firmware update, license update → 4.5 → firmware update
In one case license update failed. Got a replacement license from mikrotik. So dont do a jump to 4.5
before ensuring the license is ok, therefore you need a step at 3.30.
Thanks ste, that is exactly what I had in mind. But, Normis claims that are unnecessary steps.
Now, question is, should I trust your real life experience or officials? 
). Both ways are ok. When the license problem appears you have 72 hours to update
the license. So dont do it on friday or just before holidays. But I’ve seen no problem
with the step at 3.30.
I’ve learned with other routers that too big upgrade steps in firmware may cause problems
with configuration so I do it this way.