What is the trend - less amount of drives with higher capacity?

[Rainz]

My AS 606T is fine, but it gets no ADM updates. Since I only use it locally and have zero other functions in it but SMB I am not overly concerned about that.

However, eventually I will have to replace it, and what I am considering is a smaller variant, but with larger drives. I now have 6x6TB drives in RAID6, 24TB.
That could easily be changed for 4x10TB drives for a RAID5 at 30TB as a starting point Newer disks are supposedly more reliable, one would assume.

Is that what you guys see as well, less amount of drives?

[snapshot]

It's very much a personal choice but to some extent depends on what speed you want across your LAN. I've gone from six 6TB HDDs in RAID10 to two 18TB HDDs in RAID1 which would be much slower to access. But the new NAS also takes M.2 SSDs so the files I'm likely to access during the day are on SSD but backup files, etc. are on HDD as they should never need to be accessed (with luck). Automated processes mirror the SSD files to HDD overnight.

RAID10 is the preferred option with four large drives rather than RAID5. There's much less stress on the remaining drives if you do have to rebuild the RAID after a drive failure.

[Rainz]

I can never expect above 1Gbit on my Lan since most of my NIC's are 1Gbit NICS. My current I/O is above 100Mbit, on RAID6, sometimes higher, depending of course of the usual Windows issue with many small files or few large files. I might use NVME slots as Flash, but I do not see myself using anything but LFF drives for another decade.

I use the NAS as primary local backup. (Got a Serverbased File share that everyone work towards, it is backed up to NAS, some more important files are backed up off site)

So performance for the NAS is not really a concern, I am more focused on cost and reliability. With 6 drives on RAID6 you can have two drives going down, but not with 4 drives on Raid5. (Assuming 10 TB drives).
For that I would need more and larger drives. Alsdo there seem to be no 6 drive NAS available when using the https://www.asustor.com/services/RAID_calculator ?

[snapshot]

The RAID calculator is rubbish - no 6-bay models and only two out of four recent 8-bay.