Upgrade from Server 2.2 to 6.0.3

Hi All,

We are planning to upgrade our Couchbase Server from 2.2 to the latest.
We have 3 nodes running the couchbase server.
We want to upgrade without a downtime at all.

From the documentation i read, i understood i have to upgrade major version by major version:
2.2 -> 3.x -> 4.x -> 5.x -> 6.0.3

Does it mean i have to upgrade all the 3 nodes one by one to version 3.x, and then again to version 4.x and so on,
or i can take a node, upgrade it to version 3.x then 4.x and so on, and then move to the next node? does it matter?

And also - i try to understand what is the best & shortest way to do it:
Should i remove a node, then upgrade it and then add it again, and do it for all the nodes one by one?
Every node add & remove with rebalance is about 2.5 hours - so for every version upgrade i will need 6 rebalances (remove -> rebalance -> upgrade node -> add node -> rebalance x 3 nodes)
and 4 versions upgrade - so it is 24 reblances ==> each take 2.5 hours - so all together 60 Hours of upgrade (!!!)

Am i right? or is there a better way to handle it?