and wanted to know if it's true that desktop computer are generally more powerful/durable than laptops
It is true mostly due to the higher power limits on desktop components.
The exception to this is M1 based Apple computers. Currently the laptop M1 processor has very close single thread performance to high end desktop CPUs such as Ryzen 5000 or Intel 11th generation. This is mostly because of its advanced "5 nm" manufacturing process which is a tier above that used by Ryzen 5000 and ~2 tiers above Intel 11th generation giving it world leading energy efficiency which it can spend on such performance. Graphically desktop middle range or better GPUs out perform it by a large margin, but they do have power budgets multiple times that of the M1 which is both a CPU and GPU.
Which means, that it cannot fit such beefy graphics cards or processors as desktops can.
CPU and GPU dies of desktop computers are not
that big. They could easily fit in a reasonably sized laptop. The issue is not so much the die size limiting performance, but the die power usage. Trying to consume and dissipate 400W+ of heat in a laptop form factor is near impossible and certainly impractical for the "lap" aspect of it.
And operation at higher temperatures reduces longevity of a component.
This is technically configurable so
should not be a problem. If you are allowed to configure it is another issue. The reason laptops usually run near thermal limits is due to laptop manufacturers pushing performance over thermals. If they were to cut the power limit by half then under sustained loads the laptop will perform ~70% while operating at a much lower temperature. Instead they usually rely on thermal limits to limit power which will always go to the same toasty temperature specified by the CPU or GPU manufacturer.
3. Every component in a laptop is smaller and more fragile.
The dies are not inherently smaller. Some laptop CPUs may even be bigger than desktop counterparts due to the increased emphasis on integrated graphic performance as well as having to offer chipset functionality. By die size I am referring to the entire die package, which for modern CPUs and GPUs might be multiple physical dies that may even include memory connected via interconnect technology into a single package. They may be more fragile due to lacking an integrated heat spreader like desktop CPUs have, however desktop GPUs are in the same form factor so will be prone to the same fragility issues should the GPU addon card be flexed excessively.
2. Heat dissipation has always been an issue with laptops, especially imho with the slimer ones. Being cautious, I myself have disabled Turbo mode in the BIOS and underclocked my Dell Latitude E7440, so it is now capped @1.50 Ghz (60% of its CPU frequency / 40% when in Battery mode) by using Windows 10's Power options / Advanced settings. Also, because I do not play any modern 3D video games, I never put any strain on its Intel HD 4400 graphics subsystem, and therefore heat never builds up and the cooling fans never spin at all (or almost never)
Ideally this would be done by setting the package power limits of the CPU. This way it could still boost to most of its full speed under light, single threaded and weak GPU, work loads while not running hot if multiple cores or the IGPU are used due to hitting the power limit. I am not sure if it is possible to set power limits on most laptops.
Because I like to know what is happening when I am using my computer, I generally use HWMonitor and TrafficMonitor
For systems with Intel processors there is also Intel Power Gadget which shows a lot of detailed technical measurements for their CPUs.
