Archive can handle long-lasting tasks without any problem. It's hard to estimate how long it will take in your environment, depending on your cluster performance. In general for medium, large to super large environments it's highly recommended to place one dedicated machines for archiving only (if you don't have that already). Difference in cluster performance is significant and such approach doesn't require change in ELS licensing, since archiving machine isn't counted as data node.
That being said - I'm not sure what is the size of those indices in GB/TB. If we are talking about 500 GB, then I'd run that in single job. If it's 1-2TB or more, then maybe I'd split it into couple of tasks (2, 3 or more). How do we do that?
Let's say that we have data from 120 days that we want archive.
First you create a task that will archive data older than 30 days and wait for it to finish.
Second (without removing that archive from archive space) you can create second task, that will archive data older than 60 days. Archive will recognize that the data from 30 days is already archived, so it will focus on data 30 days+ old.
Third you can repeat the process for 90 days, and same for 120 day old data.
In that way you have the compromise of having tasks that will end in reasonable time individually and will produce compressed files that that later Customer can open. But, if you are patient enough you can run everything in single run, it will only take longer time.
Here's example how you can configure single running task:
Submit will produce warning, but you can ignore it:
Here's where you click to run it manually (note that controls will appear when you hover your cursor over them):
If you'll decide to run everything in a single task and it will take long time, then there's also a way to see what is the progress of that task, but it require console access to linux server and checking metadata files. You can write back here and I'll show you how to do that.
In future versions of Energy Logserver that information will be displayed in the archive UI, but it's not available just yet.
Good luck. Let me know if you'll need any further help or if you'll have more questions! 💪