Within a case the Pi 4 can get pretty hot pretty fast. The attached dongle also got too hot for my liking. If you do get one, just keep in mind you may have to deal with cooling issues. I ended up buying an after-market fan and heat sinks to rectify things to my satisfaction.
I had my Pi4 operated with a passive heatsink case for almost a year outdoor. Never had a single issue, even not with temperatures up to 40Ā°C environment
I am using this one (with an active fan, but disabled most of the time) and it works like the charm.
The whole case is the heatsink, and the Pi is covered pretty well:
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Whatās the name of that case or can you post a link?
Mine is from Joy-IT, but the same case is listed in other areas as well with different brand name
If you are going down that path, I like the āfull coverageā version
More metal = more surface area = more cooling.
If the design it bad, it can be counterproductive
Iāve left my RPi 4 case-less and no issues with it in the loftā¦ so far anyhow!
This is the temperature of the device running readsb (network mode - data from Airsquitter), graphs1090, the WeeWX Weather Station together with Radarbox and Planefinder feed.
Itās the active version with two fans, but running slow at 3.3V
Location is my home office
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Do you mean this as a general comment or have you done the numbers on these heatsinks?
As Iām sure you are aware, the heat transferred can be described by: Q=UA ĪT
however the expansion gets quite complicated when you allow for the complex shape of the heatsink, the temp. gradient across it and consider the different types of heat transfer.
That may or may not be really good.
The the ambient temp is 30C, thatās really good.
If the the ambient is sub-zero, Iād be looking to improve.
Yes
It does not exceed 40Ā°C during summer, where the temperature in my room can be up to 30Ā°C
Every cheap Pi fan I have ever had has failed within a year of continuous use, first they get extremely loud then they seize up.
Iāve never had a Noctua PC fan fail so I now use this Noctua 40mm 5v fan which comes with a 2 pin adapter, 150.000 h MTTF and a 6 year warranty.
RTL-SDR Blog dongle + Tripple Filtered LNA, for me it out performs the FA Pro Stick Plus with any antenna I tried, that is with only 6ft of coax.
Seeing all these recommendations for heatsinks makes me wonder how many have tried before/after comparisons or do you just fit them because it seems like a good idea? 
The reason I ask is fitting heatsinks on my Pi4 made little difference and on one Pi actually increased the temperature slightly! 
I use the PoE HAT on all my Piās and the advantage of a fan as long as its not in earshot has been invaluable for me.
Not saying all heatsinks are uselessā¦apart from the ones I tried of course! 
-=Glyn=-
I am using 3 small aluminum heatsinks on each of my two RPi 4, which keep temprature below 50Ā°C
Price of 1 pack of 3 sinks = Canadian $ 1.95
Then your comment is true, but only sometimes and not in this case.
I gave up with the stick-on heatsinks when the glue went soft on one (high ambient temp). It fell off, contacted the PCB and destroyed the Pi.
I have an aluminum case like this (the black one)
with heatsinks like this (which were included with my Pi 3 B+ starter kit)
plus I added a single 3cm exhaust fan running on 5V above the CPU. Average temperature 48.5C. This is in the tropics in SE Asia where the ambient daytime temperature is in the low 30s. The Pi sometimes gets up to 51.1 on very hot days but it never gets warmer than that. I just had my Pi open earlier and the thermal adhesive holding the heatsinks on is still doing well.
As said, one of the Pi4 i am using is operating since 15 Months. Fans are turning pretty silent, you can hear it only if no other noise source is in the room.
But i have read from other users of this case where the fans are not doing well.
I have them running on 3.3V which makes them slower and obviously more reliable
My good old Raspi3 is still operational. it was my first one with a cheap plastic case and the small heat sinks. Even with cover closed, this is still good for flight feeding, not exceeding 55Ā°C
During summer i open the case cover and it works. Not sure if a fan is overrated or not