Why would it take hours to "surgically" implant the guns? That's the whole point of robots, that they can do repetitive tasks quickly, precisely, for long periods of time before needing to rest (recharge), without injury or fatigue. Once the robots have the necessary materials and show up to the right secret facilities to get the implants, it should go quite fast. And it's not as if you have to wait on one "surgeon" with the expertise, every member of the robot army has the skills, or can download the skills to do it themselves, so you'd have thousands of them performing the surgeries.
Since the lasers are located where the "eyes", "nose", and "ears" would be, I would guess that they had sophisticated multi-spectral visual, audio, and olfactory (and perhaps taste) sensors and recording devices to spot house fires with infrared, detect smoke and carbon monoxide (or whatever affects the aliens), detect mold or insects or other pests, detect medical issues with their families, detect pipe ruptures and things in need of home repair, smell or taste how well they've cooked a meal, smell whether the space cat has taking a crap under the couch, etc. So to implant the guns they might have swapped out the sophisticated sensory package in favor of a more basic targeting sensors within the guns themselves.
You have some points.
First they got to take the brain out, and then put it somewhere else, probably the buttocks. Then they have to take the gun apart and assemble it inside the head, or take the head apart and wrap it around the guns. That takes time, and super speed would just cause harm.
This would impair the robot being operated on, if it doesn't have to be turned off entirely like you have to turn your tower off while swapping out hard drives, so self operation seems unlikely.
So unless the operation is very simple, you need a second Robot, and for the house we saw they only had one robot and he was not allowed to leave the house, on pain of being soul whipped.
Even if the surgery took half an hour. That's still half a million robots doing surgery, and then then the two robots switch and the other two switch places.
(I'm thinking of Planet of the Apes 4, where Caesar is running around with a little shopping basket. I've threatened my wife with Planet of the Apes more than once, but short of a debilitating neck injury, I'm never going to get her to watch the original move, gods forbid the Quintology and the live action TV Show. Fuck the cartoon.)
The Robots probably ran errands and did the shopping at the local market, but the dad was pretty vocal about Timmus not leaving the house. Maybe Dad was afraid that his expensive robot would get stolen if he let it out on the town under it's own recognizance. The Robots probably have an Amazon like structure where anything that would have been found at a market, could be delivered faster and cheaper.
(The wife says that she wants to watch Roddy McDowell's other movie "Bed Knobs and Broom Sticks" and that not even threats of death would bring her to willingly watch Planet of the Apes.)
Which brings us back to the question, where do these droids get 2 million military grade particle cannons from? PS... It's exactly the same weapon that they still have today? If it is, I guess that it was just seen as a vestigial organ, neither in need of replacement or upgrade?
Their brains can't be not in their heads, since their heads fly off up, up and away to far away, and it would be unwise to rely on a wireless signal tethering for miles between their brain and their gun platform, if they were actually experiencing resistance while culling the Kaylon.
2 brains? 2 personalities?
