Higher levels for resource extraction

[Mylon]

Do mineral scanners stack with robotoid facilities? I thought they did, in which case they would be worthwhile.

Changing robotoid facilities to 5/10/15 isn't recommended, because then they wouldn't be very useful unless you had 10 resource producing facilities on one planet. At 20%, it's not profitable to build one until there are 6 already operating facilties (at 5 facilities, that 20% only gives you the benefit of one more facility at a much greater cost). The value improvement option does seem useful, though. Personally, I usually don't bother researching them beyond level 1 because I find more use with monolith facilities. Sure, they're expensive, but I can build mineral miner facilities I for quick minerals and upgrade them to monolith facilities later and save myself the 325000 research points for other uses.

[Skulky]

yes, but monolith 3's take forever while a cash strapped yet research rich empire can easily increase its production by 10% + with a minimal investment in points (100k at first IIRC).

Also, not that to construct originally the scanner type facilites are much cheaper.